Re: the 2 screws on the belly: It's an easy way to do a quick sort when checking a large gun rack of SXS such as at auctions etc.
No screw is WR droplock, 1 screw is sidelock, 2 screws is the remainder.
This will not work for American guns. My Baker sidelock has no visible screws, My Lefever boxlocks have 1 screw, My Ithaca Flues boxlock has 1 screw, almost hidden by the trigger guard. An 1860's W& C Scott bar-in-wood pinfire sidelock has 2 screws. Even realizing this bar-in-wood might be considered an exception not positive it's 100% on any guns, though perhaps generally true.
As they taught us back in English Grammar, there are exceptions to all rules.
