I had this model and never noticed until now that evidently this poor lug was forgotten in a FRENCH jail.
Notice the accent over the last "e" in "Castel-Mare"?
I just always said "Castlemare" like "Hassle Jar."
If you'll notice the tagline below the name, this character was copyrighted 1966 by Famous Monsters of Filmland. Actually, he never was a character! He was just invented to sell cool models of skeletons chained to walls.
That's also why, instead of the little "legend" or story about the critter the model was based on (like Creature from the Black lagoon or King King), there's just another snapshot of an assembled model.
Overall, somehow this guy struck me as pretty cool with his whole situation. I always wondered what the story was about the single forearm bolted to the wall at the Prisoner's feet, though!