Well, I think its predecessor, the P1, was much more like the inspirational Parker 51 than the pen in the ebay link. But to the pen in question. Actually it's a P25, a very nice pen with a rolled gold cap available in blue and black. Taking advantage of the new filling system, the modern cartridge, it probably had a tough time competing with the ballpoints of the era. Maybe that's why we don't see many. Pen was made from 1961-65
I always thought that the P stood for Patronen (cartridge) but that doesn't work for the P1 which was piston filled.
The one on eBay seems to be in nice condition. Hope this helps.
--Doug