Hello Hans.
The resin (?) P2 is a model I had the luck to find, and is fascinating indeed for being hollow:
See here for more comparative pictures
Now back to the identification of the P3. I have maybe been too fast 10 min ago with the confirmation: when I bought this P3, I ruled out it as being Stanley (and wrongly agreed here above on the base of my collection file, where I have a Tipo B Stanley listed), as I identified the Stanely as being this other model in my showase:
Consistently with its description, it's a 1935 Dubonnet front suyspension car with wide body. Alfavaganza, on the bottom of page 439, discussed that on the base of the wheels, the "unknown P3" has distinctly different wheels compared to the known Stanley. gtv6-wm, can you please confirm that the wheels in your kit fit those on my model, as well as the features of the car (narrow body, cart sprung, steering rod, etc.) ?