I, too, think it a Mod 11. The "hump" is slightly different. I've seen 16 ga ammo fired in 12 guage guns only to barely get the lead a few feet down range. It's a good example of what could happen if a 12 is fired with a 20 ga shell in the bbl. Just like in the case of coach Leach, we need further details. I hope someone can let us know.