Your gun was made in early 1968 and most likely a convertible, with out the box or a letter, hard to know for certain,,,are the last three digits of the serial number marked on the face of the cylinder?? may help to know but that being said, it usually was done for the "spare" cylinder...1968 was the last year of nonprefixed serial numbers and a transition year with their numbering as you would see ( find )in a search of the RENE, jumped from #400,000 to 500,000 and even some #800,000 with a sprinkling of "D" ( duplicate) numbers and even some nickel and chrome guns thrown in....nice gun, and not that hard to find the proper "spare" cylinder ...........
