I recently looked at a 1903 22 Trainer. The receiver was marked U.S. Springfield Armory Model 1903 255,xxx, in the "fancy" script. The barrel was marked SA 10-38 below the sight, and at the base, Long Rifle Cart'ge only. It had a magazine that fit in a cutout in the floorplate.
Were there any Springfield Armory trainers that weren't Mark 2? Is this a frankenrifle?