U.S. Military M1903A4 Rifle: Remington:

All Remington 1903A4 production was in 1943 and fell between serial numbers 3407088 and 4998320. Remington made all 29,964 Model 1903A4 rifles. 1903A4 receivers were all marked MODEL 03-A3, but the markings are offset to be readable when the Redfield Junior scope mount base is installed. Some but not all Remington 1903A4 serial numbers have a Z prefix. Model 1903A4 rifles fall in three serial number blocks: 3407088 to 34427087, 4992001 to 4999045, and Z4000000 to Z4002920. It is speculated but not verified that scrapped receivers which were recovered had a letter 'A' hand stamped before the serial number.