Sounds like your friend's grandfather was pretty stupid to saw off the barrel on a fine shotgun like the Model 12. My own grandfather was equally stupid, and had sawed off the barrels on an old side by side 10 gauge.
I did not know that my Dad even had it in his possession. But when we cleaned out the basement of his home after he passed away, we found it hidden in a corner of the basement. Besides being illegal to own, the shotgun was totally ruined by rust inside the damp basement. In fact, everything my Dad had in the basement had to be thrown away, due to the damp environment corroding everything. The shotgun was already basically destroyed by the rust, and because of the barrels being sawed off, there was no option other than to dispose of it.
That model 12 was probably like my grandfather's shotgun, and was most likely sawed off back when it was still legal to do that to a shotgun.
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