Lots of Krag stocks have small letters and numbers stamped under the butt-plate, in the magazine area, and under the receiver ring.

I imagine these indicated gauging or sub-inspections.

Some hand-guards have '99' stamped on the inside. (To aid I.D.)?

There are lots of markings on Krags that are kind of mysterious now, but, probably were important 'back in the day'.

I can only help with C.B. which is often found.  He worked in the wood shop, and I can't even give you the name the initials stand for.  Perhaps a final inspector.   I think there's someone here that knows, I seem to remember reading it before.  5MF likely knows.