1 Ducat - John Frederick

John Frederick ruled Calenberg from 1665 until his death in 1679, and his reign marked a decisive Catholic interlude in a predominantly Lutheran principality — he converted in 1651 while in Italy, a move that caused persistent friction with his subjects and neighboring Protestant courts. His ducats of this period were struck at Clausthal, the principal mint serving the Harz silver and gold mining operations, though the output in gold was modest by any measure.

Welter 1662 covers multiple die marriages across the emission, and attribution to specific years within the 1673–1679 window typically depends on the date position relative to the mintmaster's mark.