Has anyone got any ideas what this is? It's been in my family for a long time as my Great Grandfather owned a antique shop in the 1900s.
Yes, Charles III was king of Spain in 1781. Not that the Chinese counterfeiters or whoever else made this knew that, or cared. It was probably blundered from 1731, as it's a pretty crude job overall. PS- note also the "RHILLIPUS" instead of "PHILLIPUS" lettering. There's another tell that the one above was "Made in China". Compare: Images borrowed from here.