2 Ducats - Joanna and Charles I

Joanna (Juana la Loca) was nominally co-ruler throughout this entire period, yet effectively imprisoned at Tordesillas from 1509 until her death in 1555 — her name on this coinage was a legal fiction sustained for decades by Charles, who needed the dynastic legitimacy her title provided. Catalonia retained its own mint and monetary privileges under the Crown of Aragon, and issues in both names were struck at Barcelona under those older Aragonese rights rather than Castilian authority.

The Cal#5 reference places this among the earliest documented gold ducats of the joint reign from the Catalan mint.