Your Model 1, 2nd Issue would have serial numbers stamped in 2 locations, on the butt as well as the inside of the right Rosewood stock. Check there to see if you can identify the number. Other than those two sn locations, there are matching assembly numbers or letters stamped on the butt frame under the right stock, on the barrel just below the forcing cone, and on the front of the cylinder. That will determine if all the major parts belong together.
As for over-stamping of the serial number, I would be surprised if the factory would do something like that, but you never say never. If the stocks are original and have a number that matches the re-stamped butt, the factory most likely did it. If there are no numbers on the stock, chances are the gun has been messed with in some way, and who knows why a serial number would be changed, maybe a "hot" gun 75 years ago. A close-up picture of the serial number might be helpful.