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. Some of these products - like this one - have precious metal content of 1000 g (one kilogram, or 1kg) of silver.
These products are rectangular in shape and are known as "gold bars"; they are cast, as their size is not suitable for regular minting techniques.
The Royal Mint says about this product:
"This significant bar is the largest cast silver bar available from The Royal Mint Refinery (RMR), containing 1 kilo (1000 g) of 999.9 silver. They are imprinted with a unique serial number and the RMR logo. The kilo silver bar offers a higher-value purchase opportunity for investors and those who wish to own and trade larger amounts of silver.
Unlike minted bars, cast bars have less intricate designs and due to the manufacturing process there can be unevenness in the finish of the bar. This reduction in the manufacturing cost is then passed on to you, resulting in a lower premium. This finish is only aesthetic and does not affect the value." | 
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