Starting in 1949 and running though the 1960s (and maybe later), Beretta made a line of boxlock over & under shotguns called the AS grades.
Most Beretta guys agree that they are the finest boxlock double barrel O/Us shotguns ever made by Beretta. They came in 12g and 20g and were offered in a handful of different grades and with a number of different options.
This is one of the more desirable grades & configurations: the ASEL 20 gauge. If you’re looking for a great O/U and you don’t mind a single trigger and pistol grip, it’s a great gun. Because it’s at auction, you may be able to get a good deal on it. I think $4000-$4500 is a fair price for this gun, so anything less than that is a good deal.