I met a fascinating gentleman last weekend who had been an armorer in the Pacific during WW II. He told me about how they collected damaged weapons from the battlefield and what they had to do to get them back on the line. When I asked him about the mis-matched Stevens and Winchester shotguns, he said that they would come in with all kinds of damage. So they would disassemble them, put all the metal parts in a cleaning bath, lay the parts out to dry and then oil. The parts were then re-assembled without much thought to matching SNs so long as they functioned properly and were safe. His opinion - and it is just an opinion, mind you - is that in his mind a mis-matched trench gun was more likely to have seen combat, rather than sitting around in arsenals, and that should account for something in the "collectability" of the guns. Kind of like buying a rebuilt jeep that had been in Normandy (if you could find one) versus one that sat in a crate in California or New York until the war ended. Just some thoughts in this newbie's mind late in the day.