Altering the composition of money has not been a rare occurrence throughout our history. From the use of cowry shells in China, to parmesan in Italy and even the recent switch to polymer bank notes in the UK, they are key historical economic milestones. This team used muon instruments at ISIS to learn more about the composition of coins from the Northumbrian King Eadberht’s time of reign
King Eadberht ruled the region of Northumbria between 737 and 758, but other than that, virtually nothing is known about him. The coin owner has collected historical coins for 20 years and brought ~70 coins to the RIKEN-RAL muon instruments at ISIS to learn more about them, and subsequently, more about the reign of King Eadberht.
The investigations into these coins used negative muons and were conducted on the RIKEN-RAL muon facility using Port4 and the MuX setup. These muons are implanted into the coin and captured by an atom. The muons emit X-rays when cascading down the atomic energy levels which are characteristic to the atom and therefore can identify it.
The collection of coins is a representative sample of the entire length of Northumbria which spanned from The North of England (areas North of the Humber River) to South-East Scotland. They are known to be from Eadberht’s time of ruling as they have his name on one side, on the other: an animal. The coins are made of an alloy that is almost completely silver and copper in composition- but their proportions are unknown. This could be key to learning more about the economic viability of King Eadbehrt's reign.
It is thought by some that, when first introduced by Eadberht, the coins had high amounts of silver in them. Over time, this was reduced, inflating their value, possibly to cover debts or cover some of the Kingdom’s expenses. The team hopes to determine the percentage of silver in the coins to answer some questions about the economy of the time.