[Hammerslagger]

I have encountered what you describe before. As I did not have possession of the pistol, but for a few minutes, I was unable to definitively form an opinion as to the origin of the receiver which was in the correct serial number range for a RR, just as yours is.

It would help greatly if you would field strip the pistol down to the receiver (including removing the grips) and get some really detailed, clear close-up pics of any and all details; especially any markings anywhere they can be found. {Put something, like a small piece of blackened masking tape over the last 2 or 3 serial # digits.}