Q:  What is a P7 PSP?

A:  The P7 PSP consists of two generations.  The first generation had what is called a protruding butt magazine release.  The second generation has a flush butt magazine release.  They look like this:

Protruding Magazine Release Gen I	Flush Magazine Release Gen II
Comparison of Magazine Release on Gen I and II

There were also some P7 models that were imported that were marked "P7 E" which were identical to the Gen II flush magazine release guns, but marked on the frame with the designation of "P7 E" to designate the European style mag release.  These were produced as late as KA date code (1990).