5 Euros - Henri I Hyla arborea - European Treefrog

Part of Luxembourg's ongoing nature series, this issue belongs to a broader European effort in the 2010s to use collector coinage as a vehicle for biodiversity awareness — the European treefrog (Hyla arborea) having suffered significant habitat loss across the continent due to wetland drainage and agricultural intensification. Luxembourg itself lists the species as protected under national law. The bimetallic format, pairing nordic gold with a sterling silver ring, was a deliberate production choice to distinguish the nature series visually from standard circulation issues.