Maker: Platignum.
This is a quintessentially low-cost pen, almost certainly intended for a school market. The point is of the cheap self-tipped sort made by folding the tines back under themselves, which give decent performance until the metal in contact with the paper wears through.
Production Run: I am guessing from the general aura of the pen I’ve got that it’s from somewhere between 1975 and 1985; this might be elevated to “informed guess” with some helium. If you know more than I do, do please let me know.
Cost When New: Even less notion than of the date. Not much, I should say.
Size: 12.5cm long capped, 13.9cm posted, 11.7 cm uncapped.
Point: Steel.
Body: Polystyrene.
Filler: Cartridge, capacity approx. 1.2 ml; this seems to be a proprietary cartridge and long out of production, but experimentation proves that the current Cross cartridge (0.6 ml) will mount to the nipple in this pen’s section.
Platignum Cadet
If you are relying on the preceding information to win a bet or impress a teacher, you should read the site’s scholarly caveat. Remember, this is the internet, and it’s full of bad information.