'former173rd' - At 78 inches long, it is likely your sling is for the Trap-Door Springfield rifle.

It is hard to tell, because of how it is folded. I suspect your sling has a seam, where two parts overlap and are sewn together?

This was commonly done to salvage leather from C.W. slings and make slings for the more modern weapons (trap-doors and Krags).

Krag slings seem to run 64 & 66 1/2 inches.