1 Mil - Meiji

The KM#Pn21 designation tells the real story here: this is a pattern piece, not a circulation issue. Japan's 1873 coinage reform, driven by the new Meiji government's push to modernize its monetary system along Western lines, involved extensive experimentation with denominations and specifications before final types were fixed. The "mil" — a decimal subdivision unfamiliar to Japanese commerce — was ultimately abandoned before reaching circulation, leaving pattern strikes as the only physical record of the denomination's brief consideration.