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Profile: The Parker “51”

(This page revised August 26, 2021)

Reference Info Index | Glossopedia  ]

"51" Advertisement, 1947 Magnifying glass
This April 1942 Parker “51” ad pro­claims, “YEARS AHEAD OF ITS TIME. For 11 years past, chem­ists and engi­neers have been col­lab­o­rat­ing to pro­duce the writ­ing masterpiece — a pen made for a ‘high ve­loc­ity’ ink — the “high velocity’ ink made for the pen.”

Logo The Fabulous “51”: When it introduced the “51” in 1941, the George S. Parker Company knew it had a winner. The pen was stylish but not flashy, durable but not clunky, and reliable but not overengineered. Over the next 31 years, the pen proved itself immensely popular. Tales are told of people who, unable to afford a whole pen, would purchase only a cap to clip in a pocket, giving the appearance of a complete pen. Parker discontinued the “51” in 1972, but “unofficial” production continued into the 1980s in Argentina, using machinery The "51" nibthat Parker had abandoned. Parker is believed to have sold between 20 and 50 million “51”s; the exact number is not known because the company apparently stopped counting after the first 12 million.

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This pen is a first-year model in Blue Cedar, with a “Wedding Band” cap.

Compared to many fountain pens, both its contemporaries and more recent models, the “51”, with its monochrome plastics and its tiny nib that lies hooded within a shell, might be considered a Plain Jane. But the “51” was not designed to be an eyecatching display piece. It was designed to be an everyday, hardworking, trouble-free, reliable writer.

Good engineering discipline dictates that form should follow function, and Parker’s engineers and stylists apparently followed that dictum. They applied the best available technology in the most effective way possible to perform the very difficult task of writing under virtually any conceivable conditions, and the result was U.S. Patent No 2,223,541, filed by Marlin S. Baker on January 6, 1939, and issued to him on December 3, 1940. The fact that so many Vacumatic-filling “51”s are still in use more than 60 years since the last one was produced is a testament to their success. 3D cutaway illustrations of the design of the “51” are given in Anatomy of a Fountain Pen IV: The Parker “51” (Aero-metric Version).

Baker’s patent, on the surface, reveals an ingenious approach to dealing with the problems confronting the pen’s design team. However, as brilliant as the design is, it was not entirely original. On June 7, 1937, an independent inventor named Russell T. Wing filed for protection on a design that covered the basic concepts of the hooded nib and ink collector, and on January 16, 1940, he received U.S. Patent No 2,187,528. Shown here are the key drawings from Wing’s (upper) and Baker’s (lower) patents.

Patent drawings

In early 1938, Wing sold exclusive manufacturing rights to Parker for a 0.27% royalty (27¢ for every $100 of wholesale goods sold) on all future “51” sales, with a minimum payment of $5,000 for the first year and $8,000 per year after the first. During the 1940s, Wing developed further improvements. In 1943, he and Parker signed an agreement with Sheaffer, forestalling pending litigation for patent infringement, under which Sheaffer, for a payment of $25,000 and royalties, was granted a license to use the collector concept that it had embodied in the conical feed used with the “TRIUMPH” point and was excused from penalties for the pens it had already sold that used the concept. (Coincidently with the execution of this agreement, Wing and Parker added a rider to their original agreement reducing the minimum annual payment to $6,000 in consideration of the additional 0.27% royalty payments to come from Sheaffer.) In 1945, the agreement was extended to Sheaffer Canada, and in 1947 Wing and Parker entered into a similar agreement with Waterman, with Wing to receive 0.27% royalties from Waterman as well.

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This illustration shows a 1948 black “51” with a Lustraloy Stacked Coin Band
cap. This and a matte Lustraloy cap with a single narrow raised band were
the only cap variations that had chrome-plated Blue Diamond clips.

Conceived to write with Parker’s innovative super-fast-drying ink, which was also dubbed “51”, the pen was styled to accommodate its necessary innards while at the same time having a pleasing appearance. It accomplishes that marriage with exquisite success. Unlike other pens of its time, including the Vacumatics that preceded it, it isn’t marbled, mottled, striated, or pearlescent. Also unlike other pens of the time, it was never offered in an imposing “oversize” version. The ”51” is smoothly streamlined and sized not to impress onlookers but rather for its ability to serve a broad spectrum of writers who could, would, and did use it, day in and day out, without having the luxury of changing pens three or four times a day on a whim. For the first six years of its existence, it came in one size only; not until 1947 did Parker make a model of a different size — and then only a shorter version, called the Demi:

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Here is a Vacumatic-filling “51” Demi, with a standard “51” for comparison.
The Demi is shorter, but its diameter is the same as that of the standard
pen, giving it a noticeably stubby appearance.

The metal cap exemplifies the pen’s advanced engineering. Embodying Parker’s proven and very attractive design for mounting a sturdy (and replaceable) clip, it slips smoothly and reliably over the shell to seat on the clutch ring (U.S. Patent No 2,278,907, by Marlin S. Baker) and then stays put in a way that was inconceivable to the makers of earlier hard-rubber slip caps. Unlike the celluloid caps of the pen’s 1940s competitors, it is split-proof, even when too forcibly installed, and it doesn’t gouge the surface of the shell. The cap is also attractive as well as practical: Parker offered it in several polished, brushed, and matte (“Lustraloy”) versions of stainless steel, as well as a bewildering array of precious-metal designs. Silver alone appeared in four different versions: polished sterling, lined sterling, hammered sterling, and coin silver. (Sterling is .925 fine, coin silver is .900 fine.) On Vacumatic-filling “51” pens with gold or gold-filled caps, the recessed area of the clutch ring is gold washed, giving an elegant two-tone appearance that complements the cap. Most gold-capped Aero-metric pens have plain stainless-steel clutch rings.

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This illustration shows a 1944 Cordovan Brown “51” with a
16K gold-filled cap with a “Feather,” or “Chevron” band.

Where did the name “51” come from? Parker completed the development of its new pen in 1939, the 51st year of the company’s existence. Rather than give the pen a name that might prove less than felicitous when translated into other languages, Parker began a decades-long tradition by choosing a number. Numbers do not require translation.

At its introduction, the “51” was placed at the top of Parker’s line, ousting the eight-year-old Vacumatic from that honored position, and it bore price tags beginning at $12.50. Like all other Parker pens priced at $8.75 and higher, the “51” was warranted for the purchaser’s lifetime and bore Parker’s Blue Diamond, the visible indication of that warranty. The first version used the Speedline version of Parker’s reliable Vacumatic filling system, with a jeweled blind cap (the double-jewel version of the “51”). Within the year, however, the United States entered World War II. The U.S. government designated certain materials, including aluminum and brass, as critical war resources. Parker redesigned the filler and the blind cap to save those metals for the war effort. Although Parker continued to produce double-jewel pens, those pens were the premier models in the “51” line, and they were made in far smaller numbers than the single-jewel version. Thus, the most common Vacumatic-filling “51”s today do not have the jeweled blind cap. (Certain colors, however, such as Nassau Green, are more common in the double-jewel version.)

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Fountain pen Magnifying glass
This illustration shows a 1946 Blue Cedar “51” with a lined sterling
cap and an undated Navy Gray single-jewel model with a matte Lustraloy
cap. The Blue Cedar pen bears the expected Blue Diamond clip, while the Navy
Gray pen has a 1939/1940 pre-production clip with no Blue Diamond.

1946 saw the introduction of Parker’s first attempt to retire the by-then ancient Vacumatic filler. In that year, along with the button-filling VS, the company brought out a new “51” that featured a spoon filler operated by a long-stroke button similar in appearance and action to the multistroke Vacumatic pump. One of the ways Parker reduced cost was to make the threaded collar that secures the filler of plastic, in a red color to distinguish it visually from the black-anodized metal collar of the Vacumatic version. When the plastic proved too fragile in real-world use, engineers replaced it with red-anodized aluminum. Because of the collar’s color, Parker designated this “51” model as the Red Band version, while the Vacumatic-filling “51” was called the Black Band version. For various reasons, the Red Band “51” was retired in 1947, making it one of Parker’s shortest lived pens.

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Fountain pen Magnifying glass

When Parker’s engineers finally did retire the Vacumatic filler, they did so only in favor of a more reliable one. Beginning in 1948 with the reduced-scale Slender (renamed the Demi after a couple of years), the “51” sported Parker’s new “Foto-Fill” system (U.S. Patent No 2,612,867), which provided improved performance at high altitude and was also easier to use. The original “51” sported a Blue Diamond clip that identified it as the rightful successor to the great Vacumatic. (After the U.S. Federal Trade Commission prohibited the offering of a warranty if a fee was charged unless the fee was decribed in type the same size as, and in close proximity to, the warranty statement itself, Parker stopped painting the clip’s diamond blue. ) With the changeover to the Foto-Fill system (soon renamed “Aero-metric”), the clip changed, too, to an arrow reminiscent of the one used on Vacumatics before the Blue Diamond made its appearance in 1939. There is more information on “51” clip variations later in this article.

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Fountain pen Magnifying glass
Here is an Aero-metric “51” Demi, with a standard “51” for comparison.
In order to improve the Demi’s asethetics, Parker’s designers made the
new version a little longer than the Vacumatic-filling Demi and a little
thinner than the standard pen.

Kenneth G. Parker, son of company founder George S. Parker and longtime CEO, was fascinated by aircraft and flying. The 1946 purchase of a new corporate plane, a shiny aluminum Beechcraft D-18S, inspired Kenneth to ask his designers for an airplane-like pen design. The result, an otherwise standard Aero-metric pen, was the famous stainless-steel Flighter, introduced in October 1949:

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In 1961, Parker tried to extend its new cartridge/converter technology to the “51”. The resulting pen was withdrawn after only two model years. Thus, not very many cartridge/converter “51”s were made, and the model is something of a rara avis in the “51” world. Most collectors today think that the pen failed because Parker cheaped out by replacing the all-important ink collector with a solid block that didn’t produce the desired writing qualities, but in my experience this is not so. I suspect that the real problem may have been high assembly costs due to the lack of any internal provision for automatically aligning the nib and feed with the shell, such as was present in the 61.

Fountain pen Magnifying glass
Fountain pen Magnifying glass

The “51” may not be every collector’s cup of tea, but it is anything but ugly. “Ugly” does not sell more than 20 million pens over a span of more than 40 years, and “ugly” does not inspire a manufacturer to reprise a design that should, by the standards of most other industries, be dead and gone. Aesthetically speaking, the ”51” (U.S. Patents Nos D116,097 and D116,098, by Kenneth S. Parker and Marlin S. Baker) is in fact one of the most elegantly beautiful fountain pens ever made and, with its hooded nib and collector, quite probably the most revolutionary since Lewis Waterman’s discovery of the channeled feed. Certainly there has been no more truly remarkable pen since its inception.

Dating a “51”

Pens made before Parker stopped date-coding its pens have a date code on the barrel. For instructions on reading this code, refer to Parker’s Date Coding Systems.

Pens made after Parker stopped using date codes (early to mid-1950s) cannot be dated to a particular year, but you can at least narrow the possible range of years. Except for a small number of cartridge/converter pens produced from 1961 to 1963, all of these undated pens are Aero-metric fillers, and Parker’s service manual describes three distinct models:

Note that not all of the differences may be identifiable on any given pen; Parker phased some of the changes in rather than making a sudden 100% switch. The clip design of the Mark III is one example of this; there exist Mark III pens with the older design having a separate celluloid jewel.

The “51” Special

In 1950, Parker introduced a reduced-cost version of the “51”. This “51” Special looks outwardly very much like a standard “51”, but it has a stainless-steel nib (called Octanium, from the total number of eight metals used in its manufacture) and the hoop filler found in the “21” and the “51” Demi (illustrated above). The filler in the “51” Special, however, is larger than that in a Demi. Other cost-saving measures were a limited choice of colors (indicated in the table below), a bright-polished stainless-steel cap, and a black cap jewel.

More on Clips

When Parker introduced the “51” in the U.S.A. in 1941, the pen bore a “Split Arrow” clip. Because all Parker pens priced at $8.75 and higher were Blue Diamond models, it follows that the “51”, introduced at a price range beginning at $12.50, was also a Blue Diamond pen. All “Split Arrow” pens appear originally to have been Vacumatic fillers. (But the converse is not necessarily true, as we shall see later.) I have seen Blue Diamond clips with three different placements of the Blue Diamond itself:

images of 51 caps, to show the clips

Most “Split Arrow” clips are gold filled. Another uncommon but not rare variant, however, is a chrome-plated Blue Diamond clip. This clip is found on coin silver caps, on brushed stainless steel Stacked Coin Band caps, and on matte Lustraloy caps with a single narrow raised band. Here is a chrome Blue Diamond clip, on a 1947 “51” with a Stacked Coin cap:

Image of 51 cap, to show the clip

An uncommon variant of the “Split Arrow” clip bears no Blue Diamond. Parker test-marketed the “51” between 1939 and 1941, and these pre-release pens bore this clip:

Image of 51 cap, to show the clip

At various times, Parker applied the Blue Diamond either as opaque paint or as translucent enamel. Either form of the color could, and did, wear away. But there are almost always traces to indicate that it was there. Some “51”s appear from time to time with no trace of blue on their “Blue Diamond” clips; it is likely that Parker sold “51”s with the diamond not colored blue after the FTC’s 1945 ruling regarding lifetime warranties:

In 1947, with the introduction of the Vacumatic-filling “51” Demi and continuing into 1948 and the transition of all “51” models to the new Aero-metric filling system, Parker reintroduced a slightly updated version of the old Art Deco clip. The redesigned clip was a virtual duplicate of the Art Deco Arrow clip that had first appeared on the Vacumatic from 1933 to 1938. (The essential difference is that the mounting ring on the ”51” version has a smooth curve without the ridges of the Vacumatic version.) The new Arrow clip was made in gold filled and chrome plated versions. Color aside, there are two variants of the Arrow clip, as shown in this picture:

images of 51 caps, to show the clips

When Parker reintroduced the Arrow clip, it was the longer version shown to the right above. The company may have begun using the long Arrow clip sometime around the end of 1946; this means that Vacumatic-filling full-size “51”s with long Arrow clips are therefore not necessarily the product of cap swapping.

Very early in the 1950s, the clip lost some length (left, above). In the mid-1960s, Parker restyled the ”51” to create the Mark II variant, giving it a new cap like that on the 61, but still with the short ”51” clip. In about 1969, the ”51” Mark III appeared with a new 61-style clip, longer even than the older long ”51” clips and attached in the same fashion as the clip on the 75, and the venerable ”51” bore this clip until it was discontinued. The image below shows Mark II (left) and Mark III (right) clips:

images of 51 caps, to show the clips


The ”51” is today one of the most popular collectible fountain pens, and its popularity led Parker in 2002 to produce a new pen, called the 51 Special Edition (SE), which looks outwardly like a double-jewel Vacumatic-filling “51” with an Empire State cap but is internally different, with a cartridge/converter filling system and an ink delivery system identical to that of the Parker 45.

Fountain pen

The best testament to the greatness of the original “51” design comes from China, where the Shanghai Hero Pen Company produces several models whose internal construction is virtually identical to that of an Aero-metric “51”. The pen shown below is a Hero 616, a “51” copy.

Fountain pen
A Note on Punctuation

Parker’s trademark for the original “51” includes quotation marks, as you see them throughout this page. As registered, the trademark for the modern 51 SE does not include the quotation marks, although Parker did include them in the pen’s barrel imprint.
A Coat of Many Colors, One by One

The “51” Mark I and Mark II versions are made of DuPont Lucite, an acrylic plastic that is remarkably tough and was in 1941 the very latest leap in materials technology as well as being the only plastic then available that could withstand the corrosive effects of ”51” ink (which was itself a market requirement). The plastic isn’t marbled, striated, or otherwise variegated because in 1941 nobody knew how to do those things with acrylics. Although the ”51” had no interestingly patterned plastics, the model was made in a great many colors. The colors on this page are divided into four groups: those of the Vacumatic-filling “51” from 1941 to 1948, those of the Aero-metric-filling “51” from 1948 to the 1969 introduction of the Mark III, those of the Mark III from 1969 to the end of the model run in 1972, and the metals that appeared on Aero-metric pens. Most of the Vacumatic colors varied from lot to lot, and some pens are now showing discoloration due to age; thus, any two pens — or even the several parts of any given pen — can have markedly different hues or shades. The pen shown here, in the highly desirable Nassau Green, shows a rare perfect color match between its shell, barrel, and blind cap:

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Fountain pen Magnifying glass

The Rage Red and Vista Blue colors were used primarily on the Parker 61, but the Mark III “51” was test marketed in these colors. The 51 SE was offered only in Vista Blue or black. Rumors persist of a different purple and another blue/green color. There were also the stainless-steel Flighter; a gold-filled model called the Signet; and a solid gold version, the Presidential.

Parker also made demonstrators for use by dealers in explaining the pen’s internal construction. The first-year “51” demonstrator, made in 1941, had a clear shell and a red collector, with a black barrel; this color choice emphasized the important features that set the “51” apart from all other fountain pens of the time. The black barrel de-emphasized the Vacumatic filler, which had been on the market for eight years and was certainly not considered novel. Later demonstrators, as shown here, were entirely clear:

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Fountain pen Magnifying glass
Fountain pen Magnifying glass
The top pen here is a 1941 (first year) demonstrator. Note the red col­lect­or. (The gold-filled cap is not orig­i­nal to this pen.) The midd­le pen, with a clear barrel, was made in 1948. The bot­tom pen is an Aero-met­ric dem­on­strat­or with no date code, made prob­ably af­ter 1952.

Colors for the Vacumatic Filling “51” (1941-1948)
Color Name (Code)

India Black India Black (11)
Dove Gray Dove Gray (01)
Burgundy Burgundy (14) — extremely rare; appears on a very small number of U.S.-made pens
Cordovan Brown Cordovan Brown (03)
Buckskin Beige (“Tan”) Buckskin Beige (“Tan”) (97)
Yellowstone (“Mustard”) Yellowstone (“Mustard”) (96)
Nassau Green Nassau Green (98)
Navy Gray Navy Gray (13) — official color in Australia; appears on a small number of U.S.-made pens
Blue Cedar Blue Cedar (02)

Colors for the Aero-metric Filling “51” Mk I and Mk II (1948-1969)
Color Name (Code)

Black Black (11)
Burgundy I Burgundy (14)
Burgundy II “Blood Red” — appears on pens made in the U.K.
Cocoa Cocoa (09)
Forest Green Forest Green (12)
Navy Gray Navy Gray (13)
Teal Blue Teal Blue (26)
Midnight Blue Midnight Blue (15)
Plum Plum (08) — Mk I only

Colors for the Squeeze Filling “51” Mk III (1969-1972)
Color Name (Code)

Black Black (11)
Charcoal Charcoal (21)
Burgundy I Burgundy (14)
Black Rage Red (23)
Navy Gray Navy Gray (13)
Olive Olive (49)
Black Vista Blue (35)
Dark Blue Dark Blue (16)

“51” Metals (not used on Vacumatic models)
Finish Name

Stainless Steel (Flighter) Brushed Stainless Steel (Flighter)
Gold Filled (Signet), Gold (Presidential) Gold Filled, with Grouped Lines (Signet)
Gold Filled (Signet), Gold (Presidential) Gold, Plain (Presidential)

  1. The information regarding the percentage of the royalty came from Wing himself, in a personal conversation with a person known to me. The remainder of the information in this paragraph is drawn from court documents in the case of Russell T. Wing and Zoe E. Wing, Petitioners, v. Commissioner of Internal Revenue, Respondent (United States Court of Appeals, Eighth Circuit, Case Number 278 F.2d 656, June 2, 1960).

  2. For the technically minded, “51” ink (U.S. Patent No 1,932,248) did not actually dry rapidly. Its chemistry, which included metallic salts and sodium hydroxide (lye), caused the ink to sink into the paper so rapidly that the ink would appear to have dried in about one-half the usual drying time of contemporaneous inks.

  3. The FTC’s original 1945 ruling forbade “unconditional” warranties altogether if there was a fee. L. E. Waterman and Parker challenged the ruling, but Waterman withdrew its petition in 1946. Parker fought on, and the resulting 1948 court judgment softened the ruling as described here. (The prohibition remained on the use of the word “unconditional.”)

  4. Color codes are taken from wall-mounted cards used by the Parker factory repair department in Janesville, Wisconsin. Olive and Charcoal appear on the card for the Mark III pen, but I have personally seen pens in neither of these colors.

  5. Although Burgundy and Navy Gray are not commonly thought to be official U.S. production colors, they are listed on the factory card from which the color codes are taken. It is possible that they were produced in small quantities as a test run as Parker prepared to introduce the Aero-metric “51”. I have seen no pens in these colors that bear date codes.

  6. This color was advertised as Blue Cedar before and during World War II; I have seen advertising from the postwar years that calls it Cedar Blue.

  7. The “51” Special was offered initially in the four noted colors. Later, Forest Green was added to the range.

The information in this article is as accurate as possible, but you should not take it as absolutely authoritative or complete. If you have additions or corrections to this page, please consider sharing them with us to improve the accuracy of our information. Color code information provided by Susan Wirth.

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