I have a MkII with an odd serial number that doesn't come up in the search function and has a letter in the first position which I haven't seen before. SN: P00064. I was trying to date the pistol and couldn't
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On the Ruger MK pistols,, the serial number is on the receiver/frame like that. When custom makers like Volquartsen build them,, they assign their own serial number to them to follow the ATF laws.