By Ron Dutcher
I have been able to find very little about this fountain pen company other than a few examples of their letterheards, and every once in a while I spot a Keystone fountain pen. All of the examples that I have seen were identical to the one in the image. Below is a scan of an envelope from my personal collection
For more information, see the entry for Soper & Sievewright in the Glossopedia.
This article is part of the Manhattan Pen Makers Project, originated by Ron L. Dutcher. Except for typographical corrections, the text is as Ron published it. Ron wanted to include photos of advertisements or pens from each maker; he had some photos, but the gallery was far from complete. Photos here are a mixture of what Ron had and what I have been able to add from my own photo library. As with other reference articles on this site, you should not take this information as absolutely authoritative or complete.