⅔ Thaler - Frederick William

The 2/3 Thaler denomination — equivalent to a Gulden — emerged as a direct response to the monetary chaos following the Thirty Years' War, when the Holy Roman Empire's fragmented coinage system made a coin pegged to the popular Dutch guilder commercially attractive. Brandenburg-Prussia adopted the format aggressively in the early 1670s under Frederick William, the Great Elector, partly to finance his shifting military alliances during the Franco-Dutch War, which began in 1672.

KM#422 spans a two-year emission, suggesting continuous production pressure rather than a single authorized striking.