Rarest Federation circulation coin 1 sen 1976 Copper planchet (Non-Magnetic), compare to common Copper-Clad Steel 1976 1 Sen (magnetic). Mintage: less than 100 units, but the actual situation of exist known pieces is far lesser than the report mintage (note: The Federation 1 Sen struck on copper since 1967 to 1973; The Copper-Clad Steel version was 1973-1988). Red brilliant uncirculated and very rare especially in this condition. 2010 Krause has increased its price especially in UNC & BU.