A Remington 11-48 "Mohawk" semi-auto shotgun.
The precursor to the 11-87, the Mohawk is one of the last long recoil shottys that Remington made. It's 12 gauge, 4+1, with a 30 inch barrel and a fixed choke.
Made from 1949 until 1968, it ranked up there with the finest shotguns of its time, and can still shoot better than many of the newer shot guns made from composite material. The only problem is that it was before gas-operated semi-auto shotguns came around (the first was the Remington 1100, introduced in 1963), and thus the recoil might be... "lively".
The stock has a few scratches and dings, about what you'd expect from a 40+ year old gun, but all metal parts look solid, and other than a good cleaning and a wee little bit of surface rust on the barrel (that I removed with a wad of steel wool and five minutes of elbow grease) I can't find any flaws.
I'll have this at the trap range by Monday, let you know it shoots.
Edited: According to Customer Service at Remington, the Serial Number puts the date of manufacture in 1959. That shotgun is 54 years old or so. Cool.