Has anybody seen similar markings on a stock like these?

[Ms15710]

Hey all,

I was wondering if any collectors have encountered markings like these on a stock before. I am accustomed to the basic wartime and postwar cartouches, including rebuilds and rack numbers (painted and stamped) but this is the first time I have seen small letter and numeral stamps. My only assumption is a rack/unit number, but I am more interested to see if others have come across similar markings.

The stock itself has the scooped clip latch cutout and faintly bears an EMcF stamp and wartime firing proof with no other markings.

Thank you!

Respectfully,
- Michael