400-yo Shipwreck Puzzle Finally Cracked After More Than 20 Years of Mystery.

Museum and university experts in Wales have worked out the combination to a brass padlock recovered from a 16th century shipwreck. Using micro CT scanning to look inside the lock's mechanism, a team from Amgueddfa Cymru and Cardiff University found that the four-letter code spells ANCE.

Metal detectorist Peter Hughes, from Maesteg, found the lock in 1999 in sand near Margam, Port Talbot. It belongs to a wider hoard from the Ann Francis, a ship caught in a storm on 28 December 1583 while returning from Spain. The lock lay close to Spanish silver coins and two coin weights, and the museum suggests it may have protected those objects or secured a chest whose contents, such as documents or textiles, did not survive. Hughes gave the hoard to Amgueddfa Cymru in 2017, and it went on display at Swansea Waterfront Museum in July 2026.

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Hughes said he spent about 20 years trying to open the lock himself by moving the dials, without success. Dr David Williams, a research associate in Cardiff University's School of Engineering, said he was sceptical at first because the scanner was not designed for such a task. He explained that micro CT scanning is similar to hospital scanning but suited to smaller items. The first scan unexpectedly showed letters, the second went badly, and a different approach on the third revealed the code. "I was blown away that we actually cracked it," Williams said.

Senior curator Alastair Willis explained why the lock was hard to solve. It has four rings with six letters each, giving 1,296 possible combinations, and the right one must line up with the loop at the top. Additional letters on the ends do not move and are unrelated to the code, which Willis said looked designed to mislead a would-be burglar.

Senior curator Siân Iles said the lock was in excellent condition and, unlike similar examples she had seen, was not corroded or in pieces. She said it "still functions as it would have done hundreds of years ago". Its position near the wreck helps date it closely. She said it was probably used on a chest or small box, and what it held is unknown.