I just acquired an OM Single Six 22 MAG, marked Ruger 22 cal Single Six, Serial 564 395. Trying to get information about it. Unusual in that it has a 22 MAG cylinder and .224 bore, but is NOT marked MAG. Any ideas on what I have? I would like to get a 22 LR cylinder - is that possible? Any idea of the year of manufacture? Can’t find the cited serial number listed in the Ruger Serial Number Look Up table (newbie here - so may not know exactly where to look!). Many thanks!