5 Euros - Willem-Alexander Wadden Sea, Silver, Colored, Netherlands

Issued as part of the Netherlands' ongoing nature-themed collector series, this piece commemorates the Wadden Sea, which gained UNESCO World Heritage status in 2009 — a designation shared with the adjoining German and Danish tidal zones. The applied color layer, added post-strike, reflects the Royal Dutch Mint's push into the colored coin market that accelerated sharply through the 2010s as collector demand for novelty issues outpaced traditional proof production.

Face value of five euros places it above legal tender thresholds for most vending and transit systems, meaning virtually none entered circulation.