I’ve got a gun as you describe. It’s a very old Stephen Grant SLE. It has a round cross-bolt that does not stick out the left side fence but does go through a superiorly placed top rib extension that has a round hole to accept the cross-bolt. There is a plug there on the left lateral/superior fence, however, that I can detect. There is also a very small screw on the left breech face, again lateral and somewhat superior (i wonder if the screw goes in a slot in the cross-bolt to keep the bolt aligned, or is it for dismantling the cross-bolt….I have no idea??). I don’t think this is called a ‘concealed’ extension per se, though. In my books, that’s what they call a Purdey 3rd bite which is completely hidden (i.e, Burrard). I’ve looked in all my books and find no mention of what we have. I’m thinking it is unamed, but don’t know for sure?? Maybe our English gunsmith friends will pipe in and enlighten us?
