I always heard unknown as well which was one of the things I thought was cool about this. Also, I assumed it was a dept store since it says 4th floor but this confirms that it wasn't just a boy's clothing store but a old school department store.
Here's some more detail about the set. From the ads I've found, a 20 card series came out every Saturday, starting April 22nd. I found an ad introducing the Boy's line of clothes on Mar. 3, 1916 and then another announcing out of business sale on November 30th and December 5th.
March 3rd - start of Boy's clothing line
April 22nd - 1st Set
April 29th - 2nd Set
May 6th - 3rd
May 13th - 4th
May 20th - 5th
May 27th - 6th
June 3rd - 7th
June 10th - 8th
June 17th - 9th
June 24th - 10th
January 1st, 1917 - Lease up - Out of Business
I attach ads from the April 28th edition (including Eddie Collins)
May19th edition of the paper which shows the 5th set (including Walter Johnson)
June 2nd edition which shows the 7th set (including Dode Paskert)
June 23rd advertising the 10th & Final set (including Honus Wagner)
