The One Hundred Pounds (£100) coin is a coin denomination issued by the Royal Mint since 2015. The format is used to mark special occasions or themes and is not intended for general circulation - which is served by a banknote of the same value instead.
The coins contain two ounces of silver (with weight slightly differing from the silver 2oz bullion coins issued for investors), but are distributed at face value - which is much higher than their intrinsic value, making them technically non-circulating legal tender (NCLT) and not bullion.
The coins are legal tender, but contrary to popular belief this does not mean that banks and retailers automatically have to accept them (in practice, they do not accept them). | 
