The watch was found by a diver off the coast of Scotland in 1970, amidst a shipwreck that is thought to date from 1653. It has been in the National Museum of Scotland's collection since then, though historians had not been able to glean much about its condition from conventional X-rays. But when the museum's researchers read about a technique called X-ray computed tomography (CT) that had been used to image a similar artefact, and they thought it might do the trick:
CT involves taking a series of slices through an object at different angles, and combining them using a computer to produce a three-dimensional reconstruction of the object's internal structure. Andrew Ramsey and his colleagues at the company X-Tek Systems in Tring, Hertfordshire, UK, had developed an improved CT technique using small yet high-voltage X-ray sources, which enabled them to obtain very high-resolution images, even when penetrating dense metal..
Any parts made of steel, including the watch's single hand as well as the studs and pins that originally held the mechanism together, have corroded away. But most of the components are brass, and in excellent condition. "The results surpassed all of our expectations," says [Museum researcher Lore]Troalen. "We never thought that so much of the mechanism would have survived."
Those scans revealed a wealth of detail to researchers, including floral engravings, Roman numerals and even the clockmaker's signature: "Niccholas Higginson of Westminster". Historical records show that Higginson was indeed making watches in Westminster, London, circa 1650.
A watch that survived a shipwreck and 300 years underwater? Not bad Mr Higginson. [Nature]