Originally Posted by Absalom

That would be a British Service model, Lend-lease, from the late months of 1943.

If by "lower left grip frame" you mean the shoulder of the grip and there is an arrow inside the C, it would be a Canadian military property stamp. (See attached, somewhat mis-stamped example)

The stamp before the U.S. on the topstrap is a "flaming bomb" ordnance mark, standard in that location. See the third photo attached to post #1744 sbove.