This gun is just a P7, not a P7M8 or a PSP.
The P7s came after the PSPs.
To quote Mas Ayoob from 2002 "The Complete Book of Handguns":
There have been a good half a dozen variations of the P7. The first model was the PSP, and many aficionados have used this appellation for all P7s with the heel magazine release like this one came with. HK sources told me that the first relatively few PSPs were found to be a little weak in some areas, and the gun was subtly redesigned into visually indistinguishable second-generation gun by the time it reached the US shores.