.45-70 box with large stenciled red C

What might the C mean on this box of reloaded unheadstamped folded head, Berdan-primed .45-70 cartridges? Condemned, Carbine, Company C, ??? The top is missing, so no makers name is available, but the cartridges look like early UMC or WRA Co. The stencil has a military look; has anyone seen a similarly stenciled box?

Load C of several different type being experimented with by a reloader, the others being A, B, etc.?
National Guard unit reloads by/for Company C?
Bubba wanted to test his stencil skills and did a C on this box for practice?

Custer left these behind when he left for the field, but later wished he had not?

All plausible explanations, but I really like the Custer association. Of course, there’s also Buffalo Bill Cody, Ike Clanton, Kid Curry, Cherokee Bill, Curly Bill Brocius, Calamity Jane, Cole Younger, Butch Cassidy, and Kit Carson, all equally likely possibilities.