Re: PPK RZM Bad Purchase
IMHO, the price was high given the condition of the gun. But alternatively, RZM guns don't turn up on every street corner, so if you want one, you take it when you can.
The authority for the 820000-845000 numbers is Walther, so I have no reason to think it is not accurate and I agree with RJay that yours is genuine.
(I don't know if it would bother you or not, but that pitting looks like blood spatter. I have seen much the same thing on guns used in suicides.)