Probably a small contract run that bypassed the usual military contract specifications. Your assumption about intended use in automatic weapons is likely accurate, IMO. The 10-round box would be just right for mixing one tracer to every 5 rounds of ball ammo, as is the usual practice in military use. Most of the Thompson mags were 20-round; most of the M3 mags were 30-round. either way one box of ball and a 10-rounder of tracer worked out nicely.
We had .45 tracer-ball ammo in Vietnam and I preferred to load my pistol with all tracers. That allowed me to see exactly where my shots were going and quickly adjust follow-up shots (the whole idea behind tracers). What I saw in Vietnam was mostly 1960s production from Federal or W-W, occasionally some older Lake City ammo, some WW2 stock still in the supply chain (all of our .50BMG was 1943-1944).
Date of manufacture is probably the period from late-Vietnam to Gulf War I. Lots of .45 pistols still in use until the mid-1990s or later, and armored vehicle crews continued using the M3A1 SMG even longer.
Interesting detail on military .45ACP ammo that not everyone is aware of. Ammo used in semi- and full-auto weapons can suffer from bullets set back into the case during feed cycles, so most military ammo was made up with asphalt cement to secure the bullets in the case mouths. Nasty, smelly, tarry stuff that could leave heavy deposits in the weapons requiring extra effort in cleaning.
Another recollection from the old days. Had a new guy assigned to my team, had to clear a structure so I went in first with the pistol ready. Up popped Mr. Charlie, my first round hit the hard-packed floor and tumbled around. The tracer element continued burning, looked for all appearances just like the fuse burning down in a hand grenade. I think the new guy had an issue with loosening sphincter!
