1 Guinea - William and Mary

William and Mary's joint coinage was constitutionally unprecedented — no English monarch had ruled alongside a consort as co-sovereign rather than consort, and the Royal Mint had no template for depicting two rulers of equal standing. The solution, placing their conjoined busts on the obverse, required a legal determination before a single die was cut.

The series spans a short window ending with Mary's death from smallpox in December 1694, after which William continued alone. Survivors of the joint issue were not recalled but simply ceased to be struck, making the five-year window the entirety of this type's production life.