The Gold Penny, or Mancus of 30 Pence, was unearthed by a treasure hunter in West Dean, on the Wiltshire and Hampshire border, in March 2020.
It was minted during the time of Ecgberht, King of the West Saxons between 802 and 839 and experts say it is the only late Anglo-Saxon gold coin held by individuals.
A total of eight other specimens held in institutions – seven in the British Museum.
The coin, which weighs 4.82g, is expected to fetch between £ 150,000 and £ 200,000 at a sale of historic coins and medals by auctioneers Dix Noonan Webb on September 8.
Peter Preston-Morley, head of the coins department at Dix Noonan Webb, said: “It’s very exciting to see this coin, this monarch’s gold coins were completely unknown until this one. be found. “
Analysis of the coin was carried out in June 2021 and shows that it is made from “high purity gold,” with low levels of silver and copper, he said.
“This composition is consistent with that of natural gold which has not been refined or artificially alloyed,” added Mr. Preston-Morley.
“Gold of such purity is particularly malleable and easy to strike, but also more prone to wear and damage.
“None of the surface marks appear to correspond to damage or tampering caused by attempts to mount the piece for use as a brooch or pendant. “
The coin was struck in a West Saxon mint, possibly Southampton or Winchester, and bears the title of King Ecgbeorht Rex around a monogram of the word Saxon.
Mr Preston-Morley said only eight other known gold coins were minted in England between 630 and 1257, these coins likely being produced for ceremonial or high status payments.
It is believed that mancus strike orders were only given on special occasions or religious events.
“This coin probably represents a mancus, a gold denomination that first appeared in central and northern Italy, but was common in England already before the year 800,” Mr. Preston said. Morley.
“Mancus would have been extremely valuable coins. “
A single mancus of gold would have bought the equivalent of 360 loaves of wheat bread, he added.
The records of Ecgberht’s reign are limited, which means that no obvious occasion for the minting of the coin has been identified.
Nor is it possible to date the coin to a more specific period of the reign, Mr Preston-Morley added.
Last August, Luke Mahoney was stunned after discovering the “greatest treasure” of his life right behind his local pub.
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The veteran detector, who runs his own metal detector shop in Suffolk, picked up £ 100,000 of Civil War silver coins from the field behind the Lindsey Rose pub.
Valuation expert Nigel Mills examined some of the coins found and said they would fetch at least £ 100,000 at auction.
The first coin was an Elizabeth I-era shilling dating from 1573-78.
Luke admitted that he and his friends stayed awake for three nights right after the discovery to watch for rival “nighthawk” detectives who might come and steal their precious find.