Flag of Guernsey
Location of Guernsey, Alderney and Sark in the English Channel. Together they form the Bailiwick of Guernsey.
History
Guernsey, Alderney, Sark and neighbouring Jersey form the Channel Islands which all have a history associated with the medieval Duchy of Normandy, of which it became part in 933. The Duchy of Normandy was a result of Viking invasions in Frankish territory and developed a mixed French-Norse culture of its own.
The most famous Duke of Normandy was William the Conqueror, who became King of England after the Norman Conquest in 1066. In 1204 France conquered all of mainland Normandy but England managed to keep the islands under its own crown. Further French attempts in 1406 and 1781 to annex the islands failed.
The Germans captured the Channel Islands during the Battle of France in summer 1940 after the British left them undefended. Because of the lack of their strategic importance, the islands were the last places in Europe to be liberated by the Allies in May 1945.
Guernsey, like Jersey, is currently most known for its financial offshoring, which constitutes 37% of its GDP. It is an independent Crown dependency and therefore not a part of the UK itself, and hence neither of the EU. The languages spoken on Guernsey are English and local Guernésiais, which is very similar to Norman dialects of French spoken on the mainland.
Currency
For centuries, Guernsey used the French Livre rather than the British Pound. Like the British Pound (Latin: Libra), the Livre was also subdivided in 20 Sous each of 12 Deniers but had lost much more value than the British Pound had over the centuries. Guernsey followed France's transition to the Franc in 1794, which happened at a rate of 1 Live 3 Deniers or 1.0125 Livre in decimals.
Copper Liard coins, worth 1/4 Sou or 1/80 of a Livre were popular on Guernsey and were revalued slightly at 1/80 of a Franc in order to make it easier to use them along with newer decimalised French coins. The Liard coins were nicknamed Doubles, as in being worth Double Denier, despite actually being worth 3 Deniers in the pre-decimal system.
With the British attempting to introduce its own currency on the Channel Islands it allowed the minting of 1, 2, 4 and 8 Doubles on Guernsey. The 4 and 8 Doubles were worth 5 and 10 Centimes of the French Franc respectively, to make it easier to mix them. With the Pound being worth 25.22 Francs and a Guernsey Penny at 8 Doubles, the British Shilling was worth 12.5 Guernsey Pennies. This rather cumbersome system ended with the devaluation of the Franc in 1921. That year the Double was revalued to 1/8 of a British Penny and fully integrated with mainland Sterling coinage.
The Guernsey Pound was decimalised between 1969 and 1971 and followed mainland coinage in terms of composition and size. Until 1981 the coins featured the bailiwick's coat of arms, after that portraits of Queen Elizabeth II were used in line with mainland coinage.
The Guernsey Pound coins and banknotes are used actively on Guernsey, but on Alderney and Sark the British Pound is the official coinage. In practice, a mix of British, Guernsey and Jersey coinage circulate on all the Channel Islands. Alderney did issue a few of its own commemoratives, but the Alderney Pound was never used for circulation.
https://en.numista.com/catalogue/guernesey-1.html