I picked up this gem from long time friend and Ruger collector on a trade, it to me is a "Hidden Gem" a 1960 BK-46 Flat Top with British Proof Marks. I have never seen another one like it, are more out there? oh im sure. maybe Chad can chim-in with what he knows. but I feel lucky to have it. I do have another old model single six with Italian proof marks. its boxed and unfired, and two cylinders. who on here has anything thing like this, speak up....knowledge is power. FNC