The P7 PT8 is purely dedicated to training and
incapable of firing a conventional 9mm cartridge. The PT8 fires a special 9mm
round made by Geco. This is the same ammunition that the MP5PT was designed
for. The most notable feature of this P7 is the big blue dot on the front of
each side of the slide.
The 8 in PT8 refers to the magazine capacity. The gun was designed and produced in 1982-83, and only 187 examples were ever manufactured. It featured the floating chamber reminiscent of the .22LR chamber P7K3 as well, for function with the special ammunition.
Thanks to HKPRO for the Pics and info. This pistol was also highlighted in the Guns & Ammo June 1984 Special Feature on the P7 available in the "P7 in Print" section of this website