Scientists Crack 400-Year-Old Code on Shipwreck Padlock

Researchers have successfully deciphered the four-letter combination of a brass padlock that was recovered from a vessel wrecked off the Welsh coast more than 400 years ago. A collaborative team of experts from Amgueddfa Cymru (Museum Wales) and Cardiff University utilized advanced micro-CT scanning technology to examine the internal mechanism of the Elizabethan artifact without causing any damage.

The padlock originally secured cargo aboard the Ann Francis, a merchant vessel that was returning from a trading voyage to Spain when it was struck by a severe storm. Driven off course by high winds on the evening of December 28, 1583, the ship ran aground and broke apart on Margam Beach, near Port Talbot.

The vessel's cargo remained buried beneath the sand for centuries before metal detectorist Peter Hughes systematically uncovered a hoard of artifacts between 1996 and 2017. While Hughes spent decades trying to manually open the intact security device, he was unable to guess the correct sequence. He described the successful breakthrough as feeling like "opening the Ark of the Covenant."

To solve the historical puzzle, conservators enlisted engineers at Cardiff University's School of Engineering. Dr. David Williams, a research associate, employed micro-computed tomography—a scanning method typically reserved for studying bones and biological tissues—to generate a detailed three-dimensional image of the lock's interior.

By analyzing the 3D scans, Dr. Williams mapped out how the internal notches aligned with the exterior rings, ultimately revealing the four-letter code: ANCE. The mechanism features four rotating rings, each bearing six different letters, creating 1,296 potential combinations alongside stationary decoy letters designed to confuse potential intruders.

Although the digital imaging successfully bypassed the physical barrier, the specific meaning behind the combination remains an open question. Experts believe the lock likely guarded a small chest or captain's box containing valuable possessions, such as Spanish silver coins, high-value textiles, or sensitive maritime correspondence.

Alastair Willis, senior curator for numismatics and the Welsh economy at Amgueddfa Cymru, noted that while Elizabethan combination locks have been discovered in Britain previously, this specimen is exceptionally well-preserved and tied directly to a securely dated shipwreck. The padlock is currently on public display at the National Waterfront Museum in Swansea as part of an exhibition running until June 2027.