Well, I went along to the auction viewing and had a good look at the 16 bore Darne. This is the first one I have handled, and it is certainly an unusual mechanism. Someone had ground off the front sling swivel, plus inletting a gold shield where the rear swivel hole had been. Makes it look more 'English' I suppose. Otherwise it was pretty good.
Barrels were clean and bright. I don't know how the barrels come off so could not see any proof marks. It certainly is a light-weight gun, easy to carry all day. This one had a huge amount of cast to suit a right hander. I will let you know what it sells for.
HB
