Potin (also known as billon) is a base metal silver-like alloy used in coins. It is typically a mixture of copper, tin and lead (in varying proportions) and it is debated whether any actual silver needs to be present. While the term billon is more commonly applied to ancient Roman coinage, potin is usually used for Greek or Celtic coinage.
Use in Celtic coinage
Iron Age class I potin (‘Thurrock’ type), c.100BC
In 1890, so-called Potin lumps were found, of which the largest weighs 59.2 kilograms (131 lb), at the Prehistoric pile dwelling settlement Alpenquai in Zürich (Vicus Turicum) in Switzerland. The pieces consist of a large number of fused Celtic coins, which are mixed with charcoal remnants. Some of the about 18,000 coins originate from the Eastern Gaul, and others are of the Zürich type, that were assigned to the local Helvetii, which date to around 100 BC. The find is so far unique, and the scientific research assumes that the melting down of the lump was not completed, therefore the aim was to form cult offerings. The site of the find was at that time at least 50 metres (164 ft) from the lake shore, and probably 1 metre (3 ft) to 3 metres (10 ft) deep in the water.
Kentish cast bronzes (historically referred to as Thurrock potins) appear to have been the first coins made in Britain dating from the end of the second century BC. They appear to have circulated mainly in Kent and were based on coins issued by Massalia (now Marseille).
“Numiswiki – Potin”. Numiswiki. Retrieved 23 November 2012.
Keltisches Geld in Zürich: Der spektakuläre «Potinklumpen». Amt für Städtebau der Stadt Zürich, Stadtarchäologie, Zürich October 2007.
Michael Nick. “75 kilogrammes of Celtic small coin – Recent research on the “Potinklumpen” from Zürich” (PDF). Ministerio de Educación, Cultura y Deporte, España. Retrieved 2014-12-12.
De Jersey, Philip (1996). Celtic Coinage in Britain. Shire Publications. p. 20. ISBN 0-7478-0325-0.
Cunliffe, Barry (2005). Iron Age Communities in Britain: An Account of England, Scotland and Wales from the Seventh Century BC until the Roman Conquest (4th ed.). Routledge. p. 133. ISBN 9780415562928.