U.S. Special Forces were known to have carried crossbows as a silent killer occasionally, most of which were crude Montagnard weapons with the rudimentary thumb trigger. I have read that at least one SF trooper carried a crossbow made by WHAM O, the toy and sporting goods manufacturer which had the more traditional trigger as yours does but I couldn't claim with any certitude that yours was military issue or even a CISO product.
the bow cable was missing before me, and its killing me not to shoot it.
There use to be a guy that made custom bow stings named Hugh. I haven't bought from him in a while but you can give him a shout at barleybow@gmail.com Barley Bow LLC
Veteran US Navy Seabees - US Army Corps of Engineers - American Legion Post 0867
" Only two defining forces have offered to die for me. 1.) Jesus Christ 2.) The American G.I. "One died for your soul, the other for your freedom! "