Thought I could clarify who THIS "Billy the Kid" is,
Tue May 1, 2012 12:28
by reading the 3 references to BTK in Fulbright's & Stehno's THE VANISHED HERD, The History of the Cherokee Strip Cowpunchers' Association & the Cattlemen & Drovers of Early-day Oklahoma.
Unfortunately those references are in the entries about Henry Brown, who WAS a member of the "Billy the Kid Gang."
So, we still don't know who identified that photo as "Billy the Kid," however, we DO know who Billy Fox is! See pp. 123-top of 127 of the above-mentioned book, and pp. 25-26 of my own ENCYCLOPEDIA OF BUFFALO HUNTERS & SKINNERS, Vol II.