I just received a reply back from Ruger customer service about my OM Single Six. I contacted them by email with the serial number and asked them to provide whatever info they could. It turns out my father bought it while we were on an extended camping / fishing trip through Canada and Montana.
This is what I got back for free, I guess I could get "the paper" for a nominal fee, but what the heck?
We have listed the information we have available on this model below.
Serial number 363351 is a Single-Six convertible, RSS-5X, .
22 Long Rifle, .22 W. M. R., model number 00212, blue, 5 1/2" barrel, manufactured and shipped in May 1963 and it shipped to Sportsmen's Supply Inc., Billings, Montana.