Hey Neal,

Thanks for the additional photo. Do the numbers on your bolt feel raised to the touch?

Looked up arc engraving, it involves a battery or electrical hook up and a fine tipped point...guessing that it is a little like welding without adding metal, just moving it. The numbers on my bolt are neatly done. They feel raised to the touch and under a 16X loupe they look like a very fine welding bead. I could be wrong

The bolt would have been done in probably 1940 or 1941, that's when my rifle was put together by the USMC.

Lancebear