I don’t know why they’re calling it an “S2”. Every Beretta’s S2 (sometimes called “SO2”) shotgun I’ve seen has been a sidelock and a 12g. This guns is neither.
It looks more look an ASEL— the boxlock version of Beretta’s S-grade sidelock shotguns. Beretta built these guns from around 1947 and into the 1960s. They came in three models: ASE, ASEL, and ASEELL.
And this gun clearly has double triggers — not a Miller single trigger like it says in the listing.
Also, if you’re thinking about bidding on it, take a long look at the photos showing the damage to the head of the stock. Fixing that problem won’t be cheap.