I came across this unfortunately small image of a man shooting trap using an adaptive device. The other shooter has a shell pouch clearly marked
UMC
The gun appears to be a Winchester 1893 or 1897 with the forend wood removed. The shooter has a harness with a loop on the end of his partially amputated left arm, and a string attached to the trigger
Interestingly, there was a report in the March 9, 1895
Forest & Stream of an armless turkey hunter
and the same (partial) article in the March 9, 1895
Sporting Life
The Sporting Life, March 09, 1895 - Page 16 - The Sporting Life Collection - LA84 Digital Library