unusual M1 rifle receiver

[RCS]

This receiver is in excellent condition and came from Rock Island Arsenal with
the original SA 4-43 dated barrel also in excellent. What is unusual is the
machining pattern on the rear tang. I did read in an older GCA Journal that
in early 1943, some receivers had the firing pin pocket cut too deep and were
reworked. Don't know if this was among that group, it sure is not common.49991499924999349994

[bruce]

Up front ... I plead ignorance! I know the small imperfection on the right side of the receiver is not normal. Does the rework consist of the small cut on the inside rear of the receiver? Sincerely. bruce.

[RCS]

Not really certain, i talked to an advance M1 collector a few years ago and showed these
photos, he said in all the years of looking at m1 rifles, he has only seen one other ! I
should have this x-rayed maybe an answer ?

[RCS]

here are additional photos of the above receiver with SA 4-43 barrel49998499995000050001