I don't think the ink stamp, on the inside of the shell by the bail, is correct for a M-1 shell. Inside paint also looks much better than outside making me think the outside has been aged to make one think it was WWII era. From the condition shown in the photos, the heat stamp should be reasonably easy to see....if no heat stamp, it's not likely a US shell, although I have seen some others post that they do have unstamped McCords. Chin strap is repo for sure. If it has a sand texture, it is post war for sure.
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