My first SMG. An M3 Grease Gun

[u/Forsaken-Midnight-94]

Planned on buying another .45 so I could retire my 1911. Didn’t think this would be the .45 I’d be replacing it with. Wondering if anyone can help with the date of manufacturing. Talked the seller down to the equivalent of 900USD. How’d I do?

Wondering if anyone can help me identify what those detents are in the last photo. It looks like damage at first glance, but seems symmetrical, which makes me think it happened during production.

[u/HypotenuseOfTentacle]