Specialists cracked the four-letter code of the Ann Francis shipwreck lock by using micro-computed tomography to examine its interior without damage. David Williams matched internal notches to external letters in a three-dimensional scan, revealing ANCE. The museum team then tested that sequence and opened the lock, as announced on 4 November 2026.
The striking detail is that the answer came from inside a small object whose lettered rings still turned after more than 400 years. You can follow the discovery from a storm off Margam to a laboratory normally used to examine bones and biological structures. The lock’s moving rings, internal notches and recorded dimensions explain how the investigation worked.
How did the scan reveal the lock’s code?
Amgueddfa Cymru and Cardiff University used micro-computed tomography to inspect the lock without damaging it. The technique produced a three-dimensional view of its interior. That gave David Williams a way to examine the relationship between the hidden mechanism and the letters visible outside.
Williams followed the internal notches in the scan and matched them to the external lettering. The correct sequence was ANCE. His work connected the position of the concealed parts with a readable combination on the surface of the lock.
The museum team then tried ANCE on the historic object. The lock opened. That practical test confirmed the sequence identified in the tomography images: the letters corresponded to a working arrangement of the mechanism.
For you, the everyday connection is turning a combination lock until its markings line up. On the Ann Francis lock, those markings were capital letters. The scan allowed Williams to work from the hidden notches toward the visible letters that controlled access.
The general mechanism helps explain why alignment mattered. In a multiple-ring combination lock, internal notches must line up with the teeth of a pin for the lock to open. The Ann Francis investigation used the relationship between internal notches and external letters to identify the required sequence.
What kind of lock came from the Ann Francis wreck?
The museum catalogue describes four freely rotating rings marked with capital letters. These rings formed the visible part of the combination system. Their movement allowed the lettering to be arranged into the sequence that eventually opened the lock.
There are 34 letter markings on the object. Of these, 24 are on the rotating rings. Another 10 appear on two fixed end plates. That distinction matters when you examine its design: the catalogue records lettering on both moving and stationary parts.
The museum identifies the material as copper alloy. News coverage describes the lock as brass. For the collection record, copper alloy is the material classification attached to the object, alongside its dimensions, weight and acquisition information.
The catalogue also notes that this mechanism type is sometimes called a Nuremberg Lock. Lettered combination locks belong to a longer history of mechanical security. Gerolamo Cardano described a combination lock in the 16th century, the same century in which the Ann Francis sank.
How did the lock become associated with the shipwreck?
The Ann Francis was returning from Spain when it encountered a storm on the evening of 28 December 1583. The ship sank off the Margam coast near Port Talbot. The lock is associated with that wreck, and its official recorded findspot is Morfa Beach, Margam.
Peter Hughes discovered most of the wreck finds with a metal detector between 1996 and 2017. His work extended over 21 years. The lock formed part of the material recovered from the shore, linking the later laboratory investigation to a long period of discovery on the beach.
Hughes recalled that the lock’s letter rings turned easily when he recovered it from the sand. More than 400 years had passed, yet the rings retained their movement. That observation gives a concrete sense of the object’s condition before its combination was identified.
Spanish silver coins and two coin-weighing weights were found near the lock. These nearby objects are part of its archaeological context. They place the small locking mechanism alongside material connected with money and the weighing of coins.
What might the lock have protected?
Curators suggest that the lock secured a small chest holding valuables. Their proposed contents include money, documents or textiles that have not survived. This is an interpretation of the object’s use, rather than an identified set of contents recovered from a chest.
The Spanish silver coins and two weighing weights found nearby help explain the interest in a possible connection with valuables. However, the proposed chest and its contents remain a curatorial interpretation. The successful opening established the lock’s combination; it did not establish what had once been stored behind it.
The object’s recorded size also belongs in this discussion. Its maximum height is 31.8 millimetres, and its weight is 28.5 grams. Those measurements give you a firmer picture of the lock than the broad description of a shipwreck treasure: this was a small piece of security hardware.
Details you won’t find in guidebooks
The laboratory setting adds an unexpected detail to the discovery. At Cardiff University, the micro-tomography equipment Williams used normally examined bones and biological structures. For this investigation, the same laboratory approach provided a view into a historic metal locking mechanism.
The lettering also deserves a closer look. J, U, W and Y do not appear among the lock’s letters. The catalogue records a particular selection of capital letters, distributed across the rotating rings and fixed plates. The working sequence ANCE came from that physical arrangement.
The catalogue’s 28.5-gram weight and 31.8-millimetre maximum height make the mechanism easier to imagine. Four freely turning rings, fixed end plates and 34 letter markings belonged to an object of those dimensions. The scan had to make that compact interior readable.
The recovery account adds another detail beyond the code itself. Hughes described rings that turned easily after their long period in the sand. Together with the museum team’s successful test of ANCE, his observation connects the recovered object’s movement with its eventual opening.
Timeline
- 28 December 1583: The Ann Francis encountered a storm while returning from Spain and sank off the Margam coast near Port Talbot.
- 1996–2017: Peter Hughes discovered most of the wreck finds with a metal detector during a period of 21 years.
- 6 May 2025: Amgueddfa Cymru purchased the lock and registered it under inventory number 2025.17H/2.6.
- 4 November 2026: Cardiff University announced the ANCE code identified through micro-tomography and the successful opening of the lock.
Where can you see the Ann Francis lock?
The lock is displayed at the National Waterfront Museum in Swansea. Its collection record identifies Morfa Beach, Margam, as the findspot. It also records the acquisition date, material and inventory number, connecting the displayed object to its documented recovery and museum history.
If you look at the lock, pay attention to the four rotating rings and the two fixed end plates. The catalogue assigns 24 letter markings to the rings and 10 to the plates. These visible details are the external counterpart to the internal notches Williams examined in the scan.
FAQ
What was the code of the Ann Francis shipwreck lock?
The four-letter code was ANCE. The museum team tested the sequence identified through tomography and opened the lock.
How did specialists discover the combination?
Amgueddfa Cymru and Cardiff University used micro-computed tomography to inspect the interior without damage. David Williams traced how internal notches aligned with external letters in the three-dimensional scan.
When did the Ann Francis sink?
The Ann Francis sank on the evening of 28 December 1583 after encountering a storm while returning from Spain. It went down off the Margam coast near Port Talbot.
Where is the Ann Francis lock displayed?
The lock is displayed at the National Waterfront Museum in Swansea. Amgueddfa Cymru purchased it on 6 May 2025.
