The Balliwick of Guernsey, a British crown dependency, is located in the English Channel just to the west of Normandy, France. Population, about 55,000. Just about all coins from Guernsey carry low values, although pre-1900 coins in good shape start to pick up substantial collector appeal. This page applies to coins dated after 1900.
All modern (post-1950) coins from Guernsey are worth a few US dollars, including Samuel's 1969 50 pence piece. For an example in fully uncirculated condition, a collector might pay as high as $10 to add it to his or her collection.
A shield with three elongated lions appears on many coins from Guernsey.
Their monetary system uses an unusual denomination known as a 'double,' with 8 doubles in a penny. 1, 2, 4, and 8 doubles dated after 1900 and before 1950 are worth a few US dollars in average circulated condition, and tens of dollars in uncirculated condition. If you have a 1917 two double coin in average circulated condition, it catalogs for $35.
Like many small modern nations, Guernsey has figured out that they can produce nice-looking coins and sell them to collectors for exorbitant prices. The value of such modern (post 1950) pieces comes from slick marketing, and not from true intrinsic value. Just about all modern coins from Guernsey are made of non-precious metal. The few that are made of gold or silver are worth their weight in the precious metal.