The production of these “Magnum Only” Single-Sixes ended sometime in August – September 1962.The 6-1/2” barrel length soon was made available in the standard “Single-Six. The “Magnum Only” marked guns came in a black and red box with a yellow wreath on top like the standard Single-Six but designated with Cat. 22 caliber only single-cylinder guns with a Magnum cylinder. 22 caliber in this case, had the last three digits of the gun’s serial number stamped on its front face, close to the cylinder base pin hole.The idea of producing these dual cylinder guns or a “convertible” came from customers requesting that Ruger retrofit their “Magnum Only” single-cylinder guns with a. 22 caliber cylinder.The extra cylinder, the. These Magnum Only guns were put in a special serial number range of their own beginning with 300000 and ending at 340XXX.About March 1961 Ruger began to produce these Magnum Only marked guns with an extra. CAL” in two lines on the left side of the cylinder frame.In early 1960 the Magnum Only guns were also made available with varnished walnut grip panels. The Magnum guns had 6-1/2 inch barrels, round loading gates, checkered black hard rubber grips, and no firing pin groove in the rear of the cylinder.They were roll-marked“RUGER SINGLE-SIX WIN.22 RF MAG. 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'.

Ruger super single six serial numbers