Sorry, I can't help with the sender's info., but as to the Hub Postage Stamp Company of Boston, they were in business in the mid-1910's (an internet search shows ads for them in Meekel's Stamp News as early as 1914.)
A public document search (below) shows the company issued stock and was incorporated in Massachusetts in 1920:

Here's an interesting side note, though. The July 4, 1914 issue of Meekel's Weekly Stamp News contains this quote:
Quote:
—The office and business of the Hub Stamp Co., Nathan Cobe, proprietor, has been sold to Mr. Barker of the New England Stamp Co. In the fall, Mr. Cobe will take a new office in Boston.
Yet as noted above, the Hub Postage Stamp Company was incorporated in 1920. Perhaps a the new name "Hub
Postage Stamp Company" was created for this new incorporation (?)