X-ray scans cracked an Elizabethan padlock’s code, revealing how a centuries-old security mechanism worked without damaging an unusually well-preserved piece of maritime history.
For more than 400 years, a brass combination lock recovered from a shipwreck off the Welsh coast kept its secret. Lost when a violent storm wrecked the Ann Francis, the remarkably well-preserved Elizabethan lock still had working letter dials, but no one knew the four-letter combination needed to open it.
Opening it more than 400 years later meant working out its four-letter code without damaging an exceptionally well-preserved Elizabethan artifact, a challenge that brought museum specialists together with researchers more accustomed to studying bones.
The dials still turned after centuries
The lock came from the Ann Francis, which was returning from Spain when a ferocious storm blew it off course on the evening of December 28, 1583. The ship wrecked on Margam Beach, near Port Talbot, leaving its extraordinary cargo buried beneath the sand for centuries.
Dredging and storms eventually stripped away layers of sand, exposing traces of the sixteenth-century hoard. Metal detectorist Peter Hughes discovered most of it over 21 years, between 1996 and 2017. The finds, recovered by Hughes and other metal detectorists, were subsequently acquired by Amgueddfa Cymru (Museum Wales).
“When I found the lock, I was immediately astonished by the incredible workmanship and its astonishing condition. When I moved the ring dials of the combination, they turned with ease after over 400 years beneath the sands, and I was left in disbelief. I also remember being left excited at the prospect of finding wonderful things from the treasure chest it once locked,” said Hughes, finder of the hoard.
What the lock once protected remains uncertain. Researchers believe it secured a small chest containing valuable items, and its position near a collection of Spanish silver coins and two coin weights recovered from the wreck offers some clues. It may have guarded those objects or a chest holding valuables that did not survive, such as documents or textiles.
X-rays reveal the lock’s hidden code
To investigate the mechanism, museum experts worked with specialists at Cardiff University using micro-CT, a form of X-ray imaging that can reveal fine details inside an object. Dr. David Williams, a postdoctoral research associate based at the Musculoskeletal Biomechanics Research Facility in the university’s School of Engineering, explained the advantage of examining the lock this way.
“Micro-CT scanning allowed us to look inside the lock without damaging it.”
The task was to connect the letters visible on the outside with the concealed parts that determined whether the lock would open. Williams could examine those relationships in the scan, then pass the combination to the museum team for the physical test.
“By creating a detailed 3D image of the internal mechanism, I could see how the notches lined up with the letters and identify the exact combination. We normally use this technology to study bones and other biological structures, so investigating a 400-year-old padlock was certainly a first for us. I had to wait until later that evening for the museum team to test the combination, so getting the message that we’d cracked it was incredibly satisfying,” said Williams.
The four letters were ANCE, and when the museum team tested the combination, the centuries-old lock opened.
“It’s not every day you get to solve a 400-year-old mystery!” Williams said.
The code’s meaning remains a mystery
Its remarkable condition and connection to a shipwreck with a known date make the lock especially valuable as a historical find. Deciphering the combination also leaves a more personal question about whoever chose those letters.
“Elizabethan combination locks are known in Britain, but this one is in exceptionally good condition and is associated with a dated wreck, making it a unique find and the code a tantalizing mystery to solve. Of course, now we’ve solved it, we are left wondering if the code meant something to its owner,” said Alastair Willis, senior curator for numismatics and the Welsh economy at Amgueddfa Cymru.
The lock is currently on display at the National Waterfront Museum in Swansea alongside other artifacts from the Ann Francis hoard. They include rare gold coins dating from the reign of Ferdinand and Isabella of Spain and a boatswain’s whistle recovered from the wreck.
Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.