Sophisticated engineering scanning tech helps archaeologists identify rare ‘ghost coin’

Related Articles

Related Articles

Sophisticated CT scanning technology normally used by researchers from WMG at the University of Warwick to assist high tech manufacturing, has helped uncover the existence of a rare silver coin called an ‘Indio’ discovered by archaeologists investigating a shipwreck off the coast of Oman.

Over 2,800 artefacts were found in the wreck, including a bronze bell with an inscription dating back to 1498, gold coins from the era and an important bronze disc embossed with the “esfera armilar” — a personal emblem of Dom Manuel I, the then-king of Portugal.

Professor Mark Williams, Head of Product Evaluation and Technologies at WMG said,

“Our precision scanning technology is normally used to solve high tech engineering problems and help create new product designs, but on this occasion our scans were able to reveal that the archaeologists had found an “extraordinarily rare silver coin” called an Indio — the rarity of which is such that it has legendary status as the ‘lost’ or ‘ghost’ coin of Dom Manuel.”

Credit : Warwick University
Credit : Warwick University

There is only one other known example of índio coin in the world, which is held within the numismatic collection of the National Historical Museum of Brazil (MHN) in Rio de Janeiro. Despite the existence of the MHN specimen, the índio, because of its extreme rarity, has assumed legendary status within the numismatic community of Portugal as the ‘lost’ or ‘ghost’ coin of Dom Manuel I.


Subscribe to more articles like this by following our Google Discovery feed - Click the follow button on your desktop or the star button on mobile. Subscribe

To ensure correct identification of the índio recovered from the site, the block within which it was contained was CT scanned at WMG, University of Warwick using the 225kV head of the Nikon CT scanner, which provides 16-micron resolution. Even with such relatively poorly preserved coins the resulting scans clearly revealed the same coat of arms and legend on the obverse matching the MHN specimen as well as the detailed description of the same coin that featured in a 1910 auction catalogue from Amsterdam.

Another of the artefacts found on the wreck site was a small ship’s bell. The bell was discovered beneath a boulder at a depth of just 4.3 metres where it had been for the past 510 years. The bell, despite being fractured in two pieces, appeared to have a raised inscription just below the shoulder containing letters and numerals that might be a clue to the identity of the ship. The problem, however, was that the inscription was barely visible beneath a thick layer of corrosion crust.

The only way to decipher what was written in the inscription without physically touching or harming the bell was by X-raying it, the bell was taken to WMG, University of Warwick. At WMG Dr Jason Warnett used non-destructive high-resolution imaging of the bell using their Nikon Metrology 320kV micro-focus X-ray (64 micron resolution) for computed tomography (CT). By CT scanning the bell before any conservation treatment was performed it was possible to reveal minute details within the inscription. Thanks to the powerful 320kV X-ray source being able to penetrate the crust the internal details were revealed.

Dr Warnett, researcher at WMG said, “It has been fantastic to work on such an exciting project, engineering skills and new technology contributing to historic archaeological discoveries like this really is the future.”

Credit : Warwick University
Credit : Warwick University

The CT scanning consisted of multiple 3.5-hour scan cycles, consisting of 3,142 individual X-ray projections. Different orientations of the bell were necessary to achieve optimum penetration whilst minimizing unwanted X-ray scatter that would obscure characters in the inscription. The scans revealed an ‘8’ and an ‘M’ that were barely visible to the naked eye. The next scan clearly revealed a ‘9’ to the left of the ‘8’, and then a final scan revealed a less apparent ‘4’ to the left of the ‘9’.

Although no other letters could be made out in addition to the ‘M’, this non-destructive imaging indicated that the inscription included a date (‘498’) that was chronologically correct with the known history of the ships squadron, which had left Lisbon in 1502.

David L. Mearns, Director of the Esmeralda Shipwreck project, who brought these priceless artefacts to WMG, commented,

“The use of CT scanning technology is fairly new to archaeological investigations but our project has proved what a powerful analytical tool it can be. Besides the bell date and indio coin revelations, the scans made by Professor Mark Williams and Dr Jay Warnett allowed us to identity all 24 silver coins within concreted clumps that would have been impossible to achieve without irreversibly damaging these rare coins.”

WARWICK UNIVERSITY

- Advertisement -

Download the HeritageDaily mobile application on iOS and Android

More on this topic

LATEST NEWS

Study Suggests the Mystery of The Lost Colony of Roanoke Solved

The Roanoke Colony refers to two colonisation attempts by Sir Walter Raleigh to establish a permanent English settlement in North America.

Drones Map High Plateaus Basin in Moroccan Atlas to Understand Human Evolution

Researchers from the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) have been using drones to create high-resolution aerial images and topographies to compile maps of the High Plateaus Basin in Moroccan Atlas.

The Kerguelen Oceanic Plateau Sheds Light on the Formation of Continents

How did the continents form? Although to a certain extent this remains an open question, the oceanic plateau of the Kerguelen Islands may well provide part of the answer, according to a French-Australian team led by the Géosciences Environnement Toulouse laboratory.

Ancient Societies Hold Lessons for Modern Cities

Today's modern cities, from Denver to Dubai, could learn a thing or two from the ancient Pueblo communities that once stretched across the southwestern United States. For starters, the more people live together, the better the living standards.

Volubilis – The Ancient Berber City

Volubilis is an archaeological site and ancient Berber city that many archaeologists believe was the capital of the Kingdom of Mauretania.

Pella – Birthplace of Alexander The Great

Pella is an archaeological site and the historical capital of the ancient kingdom of Macedon.

New Argentine fossils uncover history of celebrated conifer group

Newly unearthed, surprisingly well-preserved conifer fossils from Patagonia, Argentina, show that an endangered and celebrated group of tropical West Pacific trees has roots in the ancient supercontinent that once comprised Australia, Antarctica and South America, according to an international team of researchers.

High-tech CT reveals ancient evolutionary adaptation of extinct crocodylomorphs

The tree of life is rich in examples of species that changed from living in water to a land-based existence.

Fish fossils become buried treasure

Rare metals crucial to green industries turn out to have a surprising origin. Ancient global climate change and certain kinds of undersea geology drove fish populations to specific locations.

Archaeologists Discover Viking Toilet in Denmark

Archaeologists excavating a settlement on the Stevns Peninsula in Denmark suggests they have discovered a toilet from the Viking Age.

Popular stories