Old Model Single Six Cylinder Questions

I have some questions regarding Single Sixes. I am wondering what year Ruger began to number the Long Rifle Cylinders? I know that the Mag Cylinders are typically numbered, and that the Mag Cylinders are more commonly lost. I'd like to try and get the correct "type" of cylinder, matching the age of the revolver, and wonder if there is a time of unnumbered LR Cylinders, that would be a better match than the Newer Numbered Cylinders. I do realize that the Old Model LR Cylinders have a Firing Pin Groove between chambers. Thanks for your help.

Sometime after they starting using the XR3-RED grip frame, I think somewhere around 1962-1963 Ruger started scratching the last 3 digits of the serial number on BOTH cylinders. Sometimes the .22 l.r. would get out of the factory without getting marked but usually they both would get marked.