interesting trigger gaurd R marked.

[Col. Colt]

Chuck, I have looked at a few of these over the years - never saw it done that way...... Wartime production, or could it be from the "Final Buy" of parts for post War rebuilds? Interesting.
There is increasing interest in Post War rebuilt M1s, and perhaps that is a category for the M1903 as well.
I have a Rock Island (1918) that appears to be a Remington Post War rebuild (John Beard advises they had a contract) - Remington marked scant (M1903 only) stock, new CC bolt, replaced barrel, etc. It is marked, in front of the trigger guard "4 7 5" with the seven elevated above the "45" in the same place as the M1903A3 inspection marks. Despite the new parts, the parts are not refinished - just rebuilt. CC