Platignum was a subsidiary of the Mentmore pen company specialising in low cost fountain pens for the mass market. During the 1950s t0 1970s they were very popular with school children and young adults.
Platignum introduced a cartridge filler in 1965, this pen has a distinct late sixties or early seventies look, I think the decent quality hard plastic box makes it an early one.
The pen is unusual in that it is still in excellent condition and is an outrageous bright pink/orange/red colour. The cap and clip are finished in polished chrome. The nib is Gold plated and the plating has held up remarkably well.
Because of its colour, condition, and the box this pen could form part of a Platignum collection but could also make an unusual and attractive vintage every day writer.