Well, with that combination of characteristics it can't be a "real" S&W Model 10 because they weren't made prior to 1957 and the SN is too low for that. It still could be a .38 M&P from around 1948 that was modified sometime after 1957 and stamped "Mod 10" at that time. But I guess the first question is . . .
Are you sure it's a Smith & Wesson product? It should have the intertwined "S&W" trademark on the sideplate. On the right side, i.e., the same side, of the frame, it should have four stamped lines reading "Made In U.S.A., Marcas Registradas, Smith & Wesson, Springfield, Mass." If it's the original S&W barrel, it should say "Smith & Wesson" on the left side and ".38 S&W Special CTG" on the right side.
Given that you don't actually own the gun yet, I guess you can't post pics, but that would sure help.