Robert Bell's Sons, the Alexandria, Virginia printer, apparently printed a special batch of self-addressed envelopes, creating the above ad cover for their company and one of their non-printing products--the Falcon Stub (a style of nib for a fountain pen).
The company seems to have enjoyed a long tenure in Alexandria. The earliest reference I can find is 1834 from a Web page on the Alexandria Library site featuring, appropriately enough, a Valentine card (below) from the company.
They also offer this brief account of the company's history:
Robert Bell's Sons is listed as a printer in the 1834 Occupational Directory and located on "Green near Royal." According to the 1860 Boyd's Washington and Georgetown Directory, Robert Bell's Sons moved to 110 South Fairfax Street. It stayed at that location another 87 years listing itself as a printer, bookbinder, stationer, engraver and an office supply store.The ad cover is dated February 8, 1900. If the above information is correct about the company's longevity, and we assume they entered into business in the 1834 (may have been earlier), 24 years would elapse before the 1860 Boyd's Directory. With the additional 87 years indicated, the company would have survived well into the 20th century, to 1947. So we know they existed for at least 111 years and quite possibly more. That seems a pretty good run, especially for a small business.