Scientists crack 443-year-old shipwreck lock's code using CT scans

The brass lock remained shut since the Ann Francis sank off Wales in 1583 (Image Credit: Amgueddfa Cymru via Cardiff University)A ship returning from Spain was caught in a violent storm and wrecked off the coast of Wales in 1583. Among the objects recovered from the wreck was a brass combination lock that remained closed for more than four centuries. Researchers have now solved its four-letter code without forcing it open, using advanced CT scanning technology to examine the delicate mechanism.Cardiff University announced the discovery on November 4, 2026, following research conducted with Amgueddfa Cymru, also known as Museum Wales. The researchers successfully identified the combination as ANCE and opened the lock without damaging it. The discovery has helped solve a centuries-old puzzle, although researchers are still uncertain about what the lock originally protected and why its owner chose those four letters.A ship lost off the Welsh coastThe ship, named Ann Francis, was returning from Spain when it encountered a severe storm on December 28, 1583. Blown off course, it eventually wrecked on Margam Beach, near Port Talbot in south Wales. Much of its cargo remained buried beneath the sand for centuries. Metal detectorist Peter Hughes discovered most of the recovered treasure over 21 years, between 1996 and 2017. Storms and dredging gradually removed layers of sand at Margam Beach, exposing coins and other objects from the sixteenth-century vessel.The brass combination lock was among the recovered items. Its rotating letter rings remained movable despite spending centuries beneath the sand, but nobody could open it. The artefact was subsequently acquired by Amgueddfa Cymru and became the subject of further investigation.CT scans revealed the hidden combinationInstead of attempting to force the lock open and risk damaging it, researchers from Amgueddfa Cymru collaborated with specialists at Cardiff University to examine its internal structure. Dr David Williams, a research associate at Cardiff University's School of Engineering, used micro-CT scanning to produce detailed three-dimensional images of the lock's internal mechanism. The technology allowed researchers to examine components that could not be seen from the outside.By studying the positions of the internal notches and their alignment with the letters on the rotating rings, the team identified the four-letter combination as ANCE. Researchers then tested the combination and successfully opened the lock, confirming that their findings were correct. The process allowed them to unlock the centuries-old object without physically dismantling or damaging its mechanism.Williams explained that the scanning facility was normally used to examine bones and other biological structures, making the investigation of a historic combination lock an unusual application of the technology.What could the lock have protected?Although researchers have discovered how to open the lock, its original purpose remains a mystery. They believe it may have secured a small chest containing valuable belongings. The lock was discovered near Spanish silver coins and two coin weights recovered from the shipwreck. This has led researchers to consider whether it might have protected valuable objects or a collection of personal belongings.However, the contents of the possible chest have not been established. Researchers believe it could have contained items such as documents or textiles that have not survived the centuries since the wreck. Alastair Willis, senior curator for numismatics and the Welsh economy at Amgueddfa Cymru, said that Elizabethan combination locks were known in Britain, but this example was particularly interesting because of its condition and its connection to a shipwreck with a recorded date.Researchers are also interested in understanding whether the letters ANCE had a personal or symbolic significance for the person who originally set the combination.Historic treasure goes on displayThe brass lock is among the Ann Francis shipwreck artefacts featured in the Tides of Treasure exhibition at the National Waterfront Museum in Swansea. The collection also includes rare gold coins from the reign of Ferdinand and Isabella of Spain and a boatswain's whistle recovered from the wreck. The treasure was acquired for Wales's national collection with support from the Welsh Government.The discovery has revealed how a centuries-old combination lock worked while preserving its original mechanism. Although the meaning of its four-letter code and the identity of the person who set it remain unknown, modern scanning technology has helped researchers unlock another part of the story of the Ann Francis, more than 400 years after the ship sank.