25 Euros Faszination Licht

Austria's niobium bimetallic series, launched in 2003, was among the first in the world to exploit niobium's capacity to take on different colors through anodization — an electrolytic oxidation process that varies the oxide layer thickness to produce specific wavelengths of reflected light. The 2008 "Fascination with Light" issue used a blue anodization to evoke visible light itself, a choice that required precise voltage control during production; niobium anodization is notoriously sensitive, with small deviations producing measurable color drift across a batch.

Annual mintage was capped at 65,000 pieces.