CT scans reveal the four-letter code on a 400-year-old lock from the Ann Francis shipwreck

A brass lock that spent centuries buried in Welsh sand has finally given up its secret. Researchers used CT scans to read its four-letter combination, ANCE, without turning a single ring or risking any damage to the object.

A storm, a ship and a beach in South Wales

The lock comes from the Ann Francis, a ship returning from Spain to England in late 1583. On 28 December, a storm drove it off course and wrecked it on Margam Beach, near Port Talbot in South Wales. According to Arkeonews, the owner was Francis Shaxton, from a merchant family linked to smuggling, and court records describe disputes over ownership and accusations of organised looting after the wreck.

The cargo then lay under the sand for centuries. Metal detectorist Peter Hughes found most of the material between 1996 and 2017, including coins and other objects. Museum Wales reports about 870 gold and silver coins from Spain, Portugal, Germany and the Americas. Amgueddfa Cymru, the national museum of Wales, acquired the hoard with Welsh Government support.

How scanners read a lock without opening it

The lock is a small brass combination lock with four rotating rings, each carrying letters. Arkeonews gives its size as 31.8 millimetres tall and 28.5 grams in weight, and says the museum’s collection record calls it a type sometimes known as a Nuremberg lock. Hughes said he was astonished by the workmanship when he found it.

Teams from Amgueddfa Cymru and Cardiff University turned to micro-CT scanning, an X-ray technique that builds a detailed three-dimensional picture of an object’s insides. Dr David Williams, a research associate in Cardiff University’s School of Engineering, studied the scan images. Inside the lock, a key-shaped structure carries notches, and those notches line up with letters on the rings. That alignment revealed the combination: A, N, C, E.

The method matters as much as the result. Forcing a corroded, 400-year-old mechanism could have broken it. Scanning let the team read the code and keep the lock intact for display.

What the lock may have protected

Hughes found the lock near Spanish silver coins and two coin weights. That context suggests it may have secured a small chest of money or valuables. Nation.Cymru adds that the chest might also have held perishable items such as documents or textiles, which would not have survived in the sea and sand. The evidence cannot settle the question, because the chest itself is gone.

A code with no known meaning

Solving the lock raises a new puzzle. Alastair Willis, Senior Curator for Numismatics and the Welsh Economy at Amgueddfa Cymru, said the team is left wondering if the code meant something to its owner. Arkeonews notes that a comparable lock in the British Museum opens with MARCI, which is a recognisable word, so ANCE may or may not hide a name, an abbreviation or a personal joke. Nobody has shown which, and the letters could be arbitrary.

The lock sits in the collection of the National Waterfront Museum in Swansea. Visitors can see it alongside other Ann Francis finds, including gold coins from the reign of Ferdinand and Isabella of Spain and a boatswain’s whistle, in the Tides of Treasure display.

Why a tiny lock matters

Shipwreck finds usually tell big stories about trade and money. This one gives a rare glimpse of an ordinary Tudor-era habit: people locked their belongings and chose a code. Non-invasive scanning also gives conservators a way to study fragile metalwork without cleaning, forcing or cutting it, and the same approach could help with other sealed or corroded objects in museum collections.

The lock may be small, but it shows how a few letters can connect a 1583 storm, a Welsh beach and a modern scanner.

Sources

• Cardiff University news: CT scans help unlock 400-year-old mystery (release; page could not be fetched, details checked against the reports below)
• Nation.Cymru: Scientists crack code of 400-year-old lock found on Welsh shipwreck
• Arkeonews: CT Scans Crack the Code of a 400-Year-Old Shipwreck Lock
• Phys.org: CT scans reveal four-letter code to 400-year-old lock from Welsh shipwreck