So here's how you know you spend too much time on this stuff. eBay seller listed this snapshot as a pair of boxers ca. 1910.
I knew immediately:
--The shot is from a professional photographer: he was standing on the ring apron
--The shirtless boxer is Jack Dempsey
--The big guy in the wife-beater is 6'6" tall Big Bill Tate, Dempsey's sparring partner.
--The location is Toledo, Ohio.
--The date is June or July 1919.
--The event was Dempsey training to fight Jess Willard.
The snapshot has a matte finish and nice silvering.