An 11th century seal belonging to the Anglo-Saxon king Edward the Confessor has been rediscovered after disappearing for more than four decades.

Known as the Saint-Denis seal, it’s the best-preserved of only three surviving wax impressions of the English king and offers a sense of his governing style and influences. As such, its apparent absence from France’s National Archives in Paris caused considerable dismay among Medieval historians. It turns out nothing untoward had taken place; rather, a clerical hiccup was to blame.

Sometime between the late-1950s and the mid-1980s, the seal was separated from its original document and moved to the detached seals section of the National Archives for conservation purposes.…