The earliest Platignums I am aware of are hard rubber lever fillers, often in less usual colours like blue or olive mottled. They had perfectly usable steel nibs. Later they produced pen and pencil sets in bright celluloid colours. Again, these are perfectly adequate pens and they have become collectors items, especially in America.
Wartime and post-war pens like the Silverline and Quick Change with its variety of nibs were cheap, serviceable pens. Many have survived in good condition. Up to this point, I think Platignum stuck to their original stated intent: to provide good cheap pens. There are even were admirable bulb fillers in the Platignum stable.
It was later, during the fifties, sixties and seventies that Platignum turned out the really bad lever and cartridge fillers that are remembered today for their habit of leaking, breaking and blotting. Those pens were not only cheap, they were shoddy.
Even at that time, though, they were capable of producing good pens. I’m writing this with the Platignum Gold Nib Pressac, a squeeze filler with a durable sac. The gold nib is very pleasant, a firm medium with a modicum of feedback. This pen came in single or double jewel form, the latter known as the Deluxe. Mine is the former.
Had Platignum’s worst efforts occurred beyond living memory it might be better regarded but there are too many people around who experienced the cheap plastic horrors of the mid-century for their better pens to stand out.
To sum up, I think the company’s bad reputation is deserved, but that’s not all there is to the story.