No4 I* Butt Stock Paint

Just something I noticed the other day on my LB. It seems there was something, or two things, painted on the LHS butt of this rifle and either removed or worn away over time. On the RHS is a "US 61" mark which is still perfectly clear and not worn.

The paint left on the LHS appears in mostly yellow with a little red lower down. It is not like a band or anything around the butt and rather just splat in the middle. I feel like I can make out in the yellow something that looks like a "D" but even then you have to look at it creatively. I can't see any evidence in this area of sanding either. Looked on here for if someone else has had a similar thing and didn't find anything but interesting ZF discussions.

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Always amazes me the quality of the wood used on milsurps.
The "US 61" is probably a unit number put on for ease of finding the thing for inventory. As opposed to anything to do with our American cousins. Kind of like the white paint put on S/N's, etc. A peace time NCO quirk.

Its quite a nice gun to look at, but the barrel is meh. I figured the 'US' mark might be something like that, but what about the remnants of the other marks? Anyone have any ideas?