I have a Remington M1903, serial number 3,363,164, barrel dated 10-42, where the receiver was produced as a M1903A3, however, the dovetail for the A3 rear sight has been ground down and a 03 rear sight and handguard were applied. It is my understanding that this is one of the "fixes" used by Remington to meet its monthly production quotas while waiting for adequate supplies of the new A3 rear sight to become available.