T4P (P-Mount) Cartridges and Styli

T4P Mount, also called P Mount were used for a relatively brief period in the 1980s mostly by Japanese brands, and most commonly on (but not limited to) parallel tracking tonearms.

They were a neat idea, simplifying changing cartridges to just removing a reftting one screw - there was no need or ability to adjust alignment or tracking force as it was all pre-set. The downsides is it limited cartridge choice and arguably compromised rigidity compared to the industry standard half inch mount which has always been far more common.

Turntables with T4P mounting are recognisable as they should always have the logo on them.  

Brands that used this design for a period include: Technics (who developed the standard), Sony, Trio/Kenwood, Hitachi, Marantz, JVC, Pioneer and probably many more I've forgotten about!