The workmanship is quite crude Andy, in fact it looks to be cast from a soft metal alloy. I know the date in Roman numerals is 1480, but I would very much doubt that was the date it was made, as the style is very un-15th century. It may be rare, in that not many were made/are left, but I don't think the character is famous enough or the medal of good enough workmanship for it to be worth more than a few quid (i.e £10). Perhaps someone else will have a different opinion.