The Royal Mint of the United Kingdom, which makes the country's circulating coinage, is also very active in the bullion coinage space and issues many bullion coins which are legal tender.
Additionally, it also makes bullion which is not legal tender and is targeted at investors and not at coin collectors - such as this one.
The Royal Mint says about this product:
"Reimagined by artists through the ages to represent the nation’s values at a moment in time, Britannia has symbolised Britain for centuries. Jody Clark’s modern interpretation of the icon shows her with symbols of strength and protection, holding a trident and a shield decorated with the Union flag, and wearing a Corinthian helmet. Struck in 999 fine silver, this one-hundred-gramme bar combines beautiful design with a safeguarded investment.
The bar is imprinted with a unique serial number and comes in secure, Britannia-branded blister packaging. A clear, removable film is included on the packaging to protect the blister while in transit. It can be removed once the product has been received, without affecting the original value."
The bar is "minted" (struck using minting techniques similar to a coin, and not cast in the way that large investment products usually are). | 
Search for United Kingdom: Silver One Hundred Grams Bar - Britannia on eBay 