If it is a 52-70, than it is probably the cartridge for a sharps carbine conversion I owned once. That carbine was a military one, complete with cartouches. It has been 50 years since I owned it. I never fired it, because while I bought it at a good price - about $75.00 along with an 1895 Winchester .30-06 Carbine in beautiful shape ($150.00 for the two) from a neighbor, I couldn’t afford the loading tools that it took to make proper cartridges. I fired the Winchester and 100 light loads measureably cratered the firing pin hole, so I stopped firing it before I ruined it, and sold both to pay for some of my college expenses.
One problem and pardon my ignorance of this type of ammunition - is this cartridge an inside-primed center-fire, or a rim-fire? My carbine was converted in 1869, from a percussion breech loader, but was a center-fire conversion. If the cartridge pictured is center-fire, it could be military and for those conversions, could it not?
Not a rhetorical question - I don’t know if there was a different military version.