Just re-measured at 2 7/8" to the bottom of the rim seat. It does seem long to me too. even second guessed my gauge with Dr. Drew's 3 X 5 card method. Perhaps a rookie running the chamber bore?
Or some one took a chamber reamer to it when they finished the pistol grip.
Miller is correct about the chamber and bore stamps.
See if there is a series of numbers like 1.XXX on the barrels. That would be the weight in kilograms at time of proof. If you weigh the barrels you may find them on the light side, a sure indication of a reamer.
I went back to my source material. From an old catalog, this appears to be a Model 375. I wouldn't bet my pay on it, but is as close as I can id it.
Pete