Information on 1903A3 Springfield Armory rebuild

I have a Remington 03A3 manufactured in January 43, with a 2-43 barrel date, that was apparently rebuilt at Springfield Armory. The stock cartouche is a closed box with SA and what looks like a lower-case "d" below it. There is an upper-case "D" in the recess under the cut-off. There are no other stock markings. All of the parts appear to be Remington, except the extractor has an "S" on the underside, which I think is Smith-Corona? It came with a Hoyt 1918 sling and the oiler/cleaning kit was in the butt trap. Someone cut the top of the peep aperture to make a kind of buckhorn sight. If anyone can offer any details as to the significance of the letter markings, date of rebuild, etc, I would be grateful.