You are probably referring to the Model 422 Co2 10 shot repeating pistol, it was manufactured 1969-1973, many had a lot of problems cycling the pellets which caused them to dispatch sometimes 2 or 3 pellets at a time, very difficult to put right, they were very well made, they are normally found in very good cosmetic condition, because the owners probably stored them away because of the fault. The old Benjamins are among my favourites, I have quite a few of their repeating pistols and rifles, one of the rifles I own that impresses me most is the Model 600 Automatic, which is a front pump 25 shot semi automatic, when pumped up you get about 5 or 6 shots before needing to top it up, a design well before it’s time, made in 1930s.
Cheers, Lawrie.