I had the pleasure of shooting one a few years back. Very nice. It was for sale too for a bit less than yours however there was a crack in the wrist of the stock.
I passed on the deal though because there is ZERO support for these shotguns, fine shooters though they are. Once in a while I catch wind about a 12 gauge A302 but this is the first I have heard of someone else with direct experience with the 20 gauge. A great example of an early gas gun.
If it breaks, which it probably wont in all likelihood, then you will have a search on your hands.