We need pictures. Serial numbers for 1903 and 1903A3 stopped just short of 5,000,000, there is no Springfield (or Remington or Smith Corona) number 6001000.
RA is Remington Arms. Remington made 1903s before developing the 1903A3 and their barrels were also used as replacements.
Mark 2 is likely a Dayton Traister scope safety made to clear a scope. Not GI.
|