The gun would be a DSC gun (less likely Maritime Commission) from mid-1943. The magnas aren't necessarily much of a detriment, especially if they are reasonably early post-war diamond magnas. A soldered rather than metal-plugged hole would be more of an issue for me. I'd say that $450 is definitely $100-150 too high; for that you can get an all-original complete one in decent shape with a bit of diligent searching.