There was another discussion regarding this same topic, and the debate continues regarding this mark. The point I also made, and will continue to make, is that the mark is believed by some to read FPK, and by others it is believed to be PK.
I am of the opinion that proving whose mark it is will remain an enigma until either an undeniable document shows up to link the mark to a company, or at least until there is a common consensus regarding whether the initials are PK, or FPK.