CT Scans Reveal Code to 400-Year-Old Shipwreck Lock

A team from Cardiff University and Amgueddfa Cymru used micro-CT scans to uncover the four-letter combination on a brass lock recovered from the Ann Francis shipwreck. The code is ANCE. The scanning produced a detailed 3D image of the lock’s interior, allowing researchers to see how its internal notches aligned with the letters without handling the delicate mechanism.

The merchant ship sank in a storm on its return voyage from Spain on December 28, 1583. Metal detectorist Peter Hughes found the wreck near Margam Beach in 1998. The site yielded more than 800 gold and silver coins, as well as ship equipment, cutlery and other objects.

Hughes spent years trying to open the lock by turning its dials. David Williams, a Cardiff University engineer, said the team’s imaging approach let them identify the combination. The lock has four rotating rings, each with six letters, creating 1,296 possible combinations; fixed letters at the ends may have served as decoys.

The lock’s original purpose remains uncertain. Researchers have suggested it could have secured coins or other valuables, including textiles or maritime documents. Amgueddfa Cymru curator Alastair Willis said the discovery has prompted a new question: whether the code held meaning for its owner.

The lock remains in working condition and visitors can see it at Swansea’s National Waterfront Museum.