There are a bunch of stamp dealers covers out there. Here are three from my collection:
I don't know anything about this dealer, but I'm guessing that by using the Quaker image he was wanting to create an image of honesty in dealing, or then maybe he was a Quaker by faith. Cover posted 1901 in Toledo.
The Economist Stamp Co., was one of the older and longer running dealerships on Nassau Street.
I love this one. Note the return address. This guy was in the Army and running his stamp dealership from his barracks. Given the date of posting, he most likely was a WW I draftee. He was involved in a real saga. He got caught up in a small mutiny, court martialed, convicted, sent to Ft. Leavenworth to do his time, later exonerated, sent back to active duty and the last I could find about him, he had been transferred to Ft. Bliss, Texas. ,