Michael Metcalf, who has died aged 85, understood the quantitative significance of medieval coins long before historians or other numismatists appreciated it.

His detailed study in the 1960s of the coins of Offa, the eighth-century king of Mercia, enabled him to assert that these coins were struck in much greater numbers than anyone had realised. This in turn suggested that early Anglo-Saxon coins were far too numerous to have been reserved for the use of an elite. Instead the numbers argued for a much greater degree of Dark Age monetisation than previously assumed.

Unsurprisingly, the established orthodoxy took some time to come to terms with this, and the ensuing debates ruffled feathers. One particular exchange in Oxford in 1966 was sufficiently robust to have been reported in the national press.

With characteristic grit, Michael resisted the vigorous criticism of the most influential scholars, until the advent of the metal detector in the 80s began to confirm Michael’s arguments through the discovery of very large numbers of medieval coins from all over the country.

Metal detecting was itself then shunned by archaeologists, who, reasonably enough, feared the destruction of important sites, but gradually a more positive attitude to responsible metal detecting developed. Nowadays the Portable Antiquities Scheme records thousands of coin finds reported by detectorists every year, and the degree of monetisation in medieval England is no longer doubted.

Facebook Twitter Pinterest Michael Metcalf in Yorkshire. The advent of the metal detector in the 1980s confirmed his arguments that coins had been minted in far greater numbers during the medieval era than had previously been believed

The evidence of single coin finds was also used by Michael to map and quantify the early Anglo-Saxon gold coins (thrymsas) and silver pennies (sceattas) of the seventh and eighth centuries, resulting in his three-volume work Thrymsas and Sceattas in the Ashmolean Museum (1993-94). He had energetically collected the new finds emerging in the 80s to make the collection of the Ashmolean Museum in Oxford, where he was keeper of the Heberden coin room (1982-98), a leader in this field.

While Michael located the principal areas in which each type was struck and used, he also demonstrated that over a quarter of the English money stock consisted of similar silver pennies struck in the Low Countries, testifying to a huge balance of payments surplus probably attributable to wool exports as early as the eighth century. Anglo-continental trade links were fundamental to English wealth from at least the eighth century until our own times.

He also applied his spatial awareness and statistical skills to the late Anglo-Saxon coinage from King Edgar’s coinage reform of 973 to the Domesday Book survey of 1086. This period featured repeated reminting of the entire national currency, as well as the export to Scandinavia of huge numbers of coins as Danegeld. The coin hoards found above all in Sweden provide numerically impressive samples, though comparison with English hoards is essential.

Moreover Michael analysed more than 600 English single finds from this period in an attempt to answer a number of key questions about the nature of the circulation and the structure and distribution of the coinage in England.

He identified 39 specific questions to explore, for example, the relative importance of the different mints, the significance of foreign coin brought to England in trade, the changing volume of the currency, the distribution of single finds across the country and the variable weight-standards to which the coins were struck. The fact that Anglo-Saxon coins of different weights circulated together raises major questions: was royal authorisation more significant than intrinsic content in establishing the value of money? Questions of this sort still underpin our idea of money today.

Michael was the son of Thomas Metcalf, a Methodist minister, and Gladys (nee Moore), who had been a teacher before her marriage. The family was from Yorkshire, but moved around according to his father’s ministry, and Michael was born in Newcastle. He grew up in Keighley, West Yorkshire, where he attended the town’s grammar school, and did a year’s national service with the army before going to St John’s College, Cambridge, to study geography.

His later numismatic work often reflected his understanding of spatial and topographical approaches. His national service had taught him Russian but he was more at home with German and French. He once told a young colleague that he felt that, with a dictionary, he could manage most European languages except Hungarian, and the range of his numismatic interests and the sources he used seems to confirm this.

For his numismatic doctorate on medieval Balkan coinage, he was taught by Philip Grierson, the hugely influential Cambridge historian and numismatic scholar. This thesis was quickly published in 1965 as Coinage in the Balkans 820-1355, and was followed by updated and expanded editions in 1970 and 2016.

His interests ranged from the eastern Mediterranean through Germany to Scandinavia, north-western mainland Europe, Iberia, Italy and Britain. Just as he was quick to appreciate the importance of new finds, he was equally ready to collaborate with scientific colleagues to exploit new techniques of nondestructive chemical analysis to establish the intrinsic content of medieval coins.

Michael had been a coin collector since childhood. He assembled an impressive personal collection of sceattas. Many museums frown on curators forming personal collections, fearing a possible conflict of interest, but at the Ashmolean Museum, where Michael worked from 1963 (when he was appointed assistant keeper in the Coin Room) until his retirement in 1998, there was no such prohibition.

In fact the museum undoubtedly benefited; Michael celebrated his 65th birthday with a gift of 12 sceattas found in the Oxford region to the museum collection. In 2015 he gave the museum a further 90 carefully collected Adriatic and Balkan coins.

He became keeper of the department and a fellow of Wolfson College in 1982. He was granted the title of professor of numismatics of Oxford University in 1996. He published prolifically, including almost 250 scholarly articles, and some 23 books.

After returning happily to his Yorkshire roots in retirement, he continued writing. He never ducked controversy, or bowed to authority and reputation unless it was sustained by reason. He was wonderfully unconcerned about appearances. He was consistently kind and generous to me. His Christmas cards generally contained a theological discussion piece, based on thoughtful reading, which expressed a deeply felt and quietly radical faith.

Michael’s wife, Dorothy (nee Uren), a teacher, whom he married in 1958, died in July. He is survived by their three children, Steven, Catherine and James, four grandchildren, Lucy, Anna, Matty and Jon, and two stepgrandchildren, Morag and Rowan.

• David Michael Metcalf, numismatist, born 8 May 1933; died 25 October 2018