I recently purchased (via online auction), a Stevens 620a with all of the military stampings that are shown on the various threads on this site. I thought I was buying an aerial trainer as it was listed with a 30" barrel. Upon receiving the gun I noticed that the serial numbers on the barrel and receiver do not match, and there are no military proofs on the barrel. Luckily I didn't pay a whole bunch for it, but unfortunately, as it is unmatching, it doesn't quite fit my collection. I won the auction at $200, but the shipping and fees brought it up to $300. Needless to say, I was ****ed, but I did fail to ask about the serials so I suppose it was my fault. The receiver and buttstock are definitely from a trench gun. It even has the correct sling swivel cutout on the bottom. I am looking for your opinions of my options. Should I:
1) Sell it to a collector who might have the correct parts to put it back together and cut my losses.
2) Hack off the barrel and buy a reproduction heat shield and bayonet lug from Numrich and have fun with it.
3) Something else.

I'm sure that being a previous military issue receiver it has some value. Any idea what the going rate for these are?

Thanks for your ideas!