This picture was taken by the famous photographer Mumpher, apparently before Joseph Sinex died on 6 October 1892.
Thanks to Thom Boynton for the picture! He also sent the following notes, derived from looking at the picture with a magnifying glass.
(from left to right)
first man is wearing an unusual hat
second man is wearing a Georgia printed band around his hat with what appears to be a Confederate Jacket with UCV Ribbons
third man is also wearing a UCV ribbon
fourth man is just standing there
fifth man, shaking hands, is wearing a UCV Ribbon of Crossed Cannons
behind the fifth man, the man waving the white surrender flag is a Confederate
sixth man, shaking hands, may possibly be another member of the 91st PA
seventh man, I believe is wearing a UCV badge (he has a heart on his hat)
eighth man (in the center of the monument), in dark clothing and a dark hat, is wearing a UCV ribbon and a Southern Cross Medal on his jacket
ninth man, in a white shirt, is not wearing any medals or ribbons
tenth man, who is short, with a hat, is wearing a Union Star Medal
eleventh man, holding his hat over his head is Lieutenant Colonel Joseph Sinex of the 91st Pennsylvania
twelfth man, at the farthest right, is his brother Robert Sinex
both Sinex's are wearing ribbons and medals (they also posed together in the 1889 Gettysburg monument dedication picture)
men sitting on the ground, can't see any ribbons to identify them