Our latest release, the 2022 St George and the Dragon Bi-Metallic Gold Sovereign Range, are the world’s first gold sovereign coins to be struck using two types of solid 22 carat gold, also known as bi-metallic. We are already familiar with bi-metallic coins in circulation. However, this is the first time this technically demanding form of striking has been attempted with gold coins.
In our latest blog, we will be exploring the process of striking bi-metallic coins.
History of Bi-Metallic Coins
Generally speaking, bi-metallic coins are coins that are produced using two metals or alloys, usually created with an outer ring around a contrasting centre. The striking of these coins dates back to the 17th century. During the reign of Charles I, the English Rose Farthing 1625-1649 was produced with a brass wedge inserted into the copper as an anti-forgery device. Also, in Germany in 1730, a silver token was struck with a centre plug made of copper.
The striking of bi-metallic coins and medallions became increasingly popular throughout the 19th and 20th centuries, and the coins are minted using many different combinations of precious and base metals, such as gold and silver, yellow and white gold, silver and nickel, silver and titanium, and combinations of brass or copper and nickel etc.
Examples of Bi-Metallic Coins
Bi-metallic coins have been in circulation since 1982, with the issue of the Italian 500 lire. Since then, more than 117 countries have produced their own circulating bi-metallic coins. For instance, the United Kingdom issued a bi-metallic £2 coin in 1997 and a bi-metallic £1 coin in 2017, both of which are still in circulation today. The Eurozone also has bi-metallic €1 and €2 coins which have been in circulation since 2002.
Other examples of bi-metallic circulation coins include the 5-dirhams coin in Morocco, the 10-francs coin in France, the 10 baht in Thailand, the $10 coin in Hong Kong, the $2 coin in Canada, the 100 and 200 forint coin in Hungary, the 1 real coin in Brazil, the 10 and 20 peso coins in the Philippines, the 10 and 20 rupee coins in India, the 1-dollar coin in Singapore, the 500 yen coin in Japan, and the 500-colones coin in Costa Rica.
The Striking of Bi-Metallic Coins
The earliest coins that might be considered bi-metallic were created as far back as Roman times by coating one metal with another to make a coin appear more valuable. This was usually done to disguise debased coinage, so for example by using a copper core and dipping it in silver. The later coins of Henry VIII of England were gradually debased, and to make them appear to contain more silver, they were either silver washed or soaked in a weak acid solution to breakdown some of the surface copper.
The earliest examples of bi-metallic coins where both metals were visible in the coin blank, were created by forcing wedges or plugs of one metal into a solid bar or coin blank of another metal.
Today, modern minting technology allows for a large central section of one metal with the outer ring of another metal. The external ring is created by a multiple-die progressive tool which pierces out the centre hole before blanking from a strip. The inner piece is made the same as an ordinary coin, however, there is special milling applied to the edges. When both are struck by the assembling press, the two are effectively locked together, with the special milling working similarly to a tongue and groove, which ensures that the two metals stay in place and do not fall apart.
The beautiful 2022 St George and the Dragon Bi-Metallic Gold Sovereign Range has been created with an outer ring of solid 22 carat rose gold containing the coin legend and an inner section containing the main design in solid 22 carat yellow gold. Browse them HERE.