Groat - Peter of Coimbra Barcelona

Peter of Coimbra's coinage exists because of a constitutional crisis. When the Catalan Generalitat revolted against John II of Aragon in 1462, they needed a king — and settled on Henry IV of Castile, who proved useless and was deposed in absentia by 1463. Peter, Constable of Portugal, was their second choice: a compromise candidate with enough dynastic credibility to legitimize the rebellion but no real power base of his own. His reign lasted until his death in 1466, and the coinage struck in his name spans almost exactly that window.

The series is scarce precisely because the institutional backing behind it kept collapsing.