MUSEUM USES
X-RAY COMPUTED
TOMOGRAPHY
TO INVESTIGATE
COIN HOARD FROM
ROMAN EMPIRE
Two Roman coin hoards were declared treasure
on 9 October 2023 by the Assistant Coroner for
North Wales (East and Central), Kate Robertson.
The hoards, an archaeological term for a collection
of valuable objects or artifacts, were discovered by
metal detectorists David Moss and Tom Taylor in
Caerhun Community, Conwy, during the winter of
2018–2019. The larger hoard (Treasure Case 19.01)
was found in a ceramic vessel. It contained 2733
coins, a mix of silver denarii minted between 32 BC
and AD 235, as well as silver and copper-alloy radi-
ates (also known as antoniniani) struck between
AD 215 and 270. The copper-alloy coins appear to
have been put loosely in the pot, but most of the
silver coins were held in two leather bags, which
were placed at the very top of the hoard. The
smaller hoard (Treasure Case 19.03) comprises 37
silver denarii, ranging in date from 32 BC to AD 221,
which were found scattered across a small area in
the immediate vicinity of the larger hoard.
When the finders discovered the larger hoard,
they carefully excavated the pot, before wrapping it
in bandages and reporting both hoards to Dr. Susie
White, Finds Officer for the Portable Antiquities
Scheme in Wales (PAS Cymru) based at Wrexham
County Borough Museum &Archives.
“People do not realize the amount of work that
goes on behind the scenes at the national museum,
from excavating the coins, to looking after them and
identifying them so they can be reported on as trea-
sure…it’s a huge process to be able to see the work
unfold…to be involved at first hand as finders is an
incredible experience,” said Moss.
The hoards were then taken to Amgueddfa
Cymru – Museum Wales for micro-excavation and
identification.
“In the conservation lab, investigation at the top
of the pot quickly revealed that some of the coins
had been in bags made from extremely thin leather,
traces of which remained. It is very rare for organic
materials such as this to survive in the soil. The
surviving fragments, which included two fragments
of a stitched seam, were preserved and will provide
information about the type of leather used and how
the bags were made,” said Louise Mumford, Senior
Conservator of Archaeology at Amgueddfa Cymru.
TWI Technology Centre Wales in Port Talbot has
been supporting Cardiff Museum in the investi-
gation of the Roman coin hoard by using its X-ray
computed tomography (XCT) system to scan the
larger hoard in the ceramic vessel. XCT was used
to see whether more information could be gleaned
before extraction of the coins began.
Consultant engineer at TWI, Ian Nicholson,
said, “Our main focus is to provide our services for
industry. However, we also like to support nonin-
dustry projects. Radiography was the only inspection
technique that had the potential to volumetrically
reveal the inside of the coin hoard without damaging
it. Our state-of-the-art computer tomography inspec-
tion equipment uses high X-ray energy to penetrate
thick metals, which is typically four times greater
SCANNER
Two Roman coin
hoards were found
in Conwy Valley,
Wales: (a) larger
Roman coin hoard
found in ceramic
vessel (b) silver coins
found in the smaller
hoard.
8
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2401 ME January.indd 8 12/20/23 8:01 AM

than the X-ray energies that dentists and
hospitals use. We found the inspection
challenge interesting and valuable when
Amgueddfa Cymru – Museum Wales
approached us—it was a nice change
from inspecting aeroplane parts. Using
our equipment, we were able to deter-
mine that there were coins at various
locations in the bag. The coins were so
densely packed in the center of the pot
that even our high-radiation energies
could not penetrate through the entire
pot. Nevertheless, we could reveal some
of the layout of the coins and confirm
it wasn’t only the top of the pot where
coins had been cached.”
The scan of the larger hoard found no
evidence of further bags in the pot below
the two visible at the top, and this proved
to be correct as the pot was emptied.
Along with the CT scans, a series of
photographs and 3D models were
created during the micro-excavation of
the hoard. These will be used in further
research, publications, and displays.
Taking the coins out in layers revealed
that the older coins were generally closer
to the bottom while the last coins of the
hoard were found in the upper layers. The
hoard was probably buried in AD 270
at a time when the Roman Empire was
split between the Central Empire and the
Gallic Empire, which included Britain. The
final coins in this hoard were issued during
the reigns of Quintillus (AD 270) and
Victorinus (AD 269–271).
The smaller hoard was probably
buried in the AD 220s. The two hoards
were found close to the remains of a
Roman building, which was excavated in
2013 and identified as a possible temple
dating to the third century AD. The
discovery of these hoards supports this
suggestion. It is very likely that the hoards
were deposited here because of the reli-
gious significance of the site, perhaps as
votive offerings, or for safekeeping under
the protection of the temple’s deity. The
coins may have belonged to soldiers
at the nearby Roman fort of Canovium
(located near Caerhun).
INDUSTRYNEWS
|
SCANNER
DATAFACTS |
MAJOR CAUSES OF TRAIN DERAILMENTS
From 2018–2022, detail fractures were responsible for as many as 222 derailments and damage
cost of US$79 million. Transverse/compound fissures (TF) were responsible for 77 derailments
and US$21 million in damage, and vertical split head (VSH) defects caused 83 derailments and
~US$20 million in damage. These three defects combined, therefore, caused as many as ~80
derailments per year and ~US$25 million in damage per year. The detection and quantification
of these flaws is clearly of importance to railroad safety and efficiency.
Source: Federal Railroad Association’s Safety Statistics. For more information, see the paper by Huang and Lanza di
Scalea on page 51.
Transverse/compound fissures Vertical split head defects Detail fractures
Example 2D image
slice extracted
from acquired
X-ray computed
tomography data
volume.
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