Unusual M1903 Stock Stamp

I was recently gifted a M1903 (9/19 barrel date; SN 1095026) that is a post war rebuild - maybe even a CMP issue. It has a scant stock with no markings except that on the tip of the stock is an anchor with the letters US, one on each side. I have both Campbell's '03 Springfields and Poyer's The Model 1903 Springfield Rifle and its Variations, but neither book mentions this stamp. Searches on the Google have not provided any insight. I'm stumped and would appreciate any information.

Thanks in advance,
Jim

Interesting, and new to me as well. No mention of this in the Brophy book either.
I could only speculate since the scants were replacements, this stamp was applied on a ship or navy depot.

I have this stamp before also on a scant stock - no way of knowing but I would guess contractor mark before USN