Re-Stamped Serial Number on Model 11?

[03A3forpigs]

My buddy has a short barreled (18 inch) Model 11 with what appears to have a restamped serial number. The number is 1212XX. The gun has the ordinance bomb and FJA on the stock but none of the other markings on the reciever or barrel. It has a duck scene on the side with the serial number and a pheasent on the other. I have looked at a bunch of pictures and none of the stamping of the serial numbers looks like this gun. Anyone have any idea why it would be like this?