22 “Magnum Only” around June of that same year. 22 Magnum cartridge was introduced by Winchester in 1959.Ruger introduced its Single-Six single action revolver in. GENERALOVERVIEW Old Model Single Six-Serial Number | Ruger Forum RUGEROLDMODELSINGLE-SIX “MAGNUM ONLY” REVOLVERS
Not too many of that serial number range, and perhaps 5000 or so were convertibles, having the 'extra'.
