From what I can tell the Mark I, II, III, and IV were made in very small numbers(around 500 each) and used by Russian biathalon shooters. They shot VERY well and when found for sale were usually cheap, but seem to bring a decent price now. The MC2(or something like that) was mass produced and very cheap. $300 seems to be the high end of the price range for them. Quality of workmanship was not very good, but they supposedly shot rather well anyway. It requires a custom made base, or drilling and tapping the receiver to mount a scope. They were meant for biathalon shooting and the sights they used mounted to the side of the receiver instead of the top.