25 ECU - Beatrix Europa Conference in Amsterdam; with town-arms

The 1990 Amsterdam European Council summit was a pivotal moment in the road to Maastricht — it was here that the Netherlands, holding the EU presidency, pushed hard to accelerate Economic and Monetary Union negotiations, laying groundwork for the treaty signed fourteen months later. The Dutch government issued commemorative ECU pieces to mark the occasion, a practice several member states had adopted to promote the as-yet-hypothetical common currency to skeptical publics.

The X# prefix in the reference confirms this as a non-circulating collector piece rather than an official monetary instrument — the ECU itself never achieved legal tender status in coin form in the Netherlands.