Like many other mints, the Royal Mint issues bullion coins in precious metals, having much higher intrinsic value than their face value. Most of these by tradition are measured in troy ounces of fractions thereof, but the mint also introduced metric coins measuring one kilogram of pure metal (they are actually fractionally heavier as a whole, to account for the small amount of other metal in the alloy).
The 1 kg silver coins are denominated as Five Hundred Pounds (£500), although their intrinsic (bullion) value is much higher than their face value. The coins vary in design depending on the occasion (they are "one-year" types usually issued in parallel with smaller denominations with the same reverse designs).
The coins are legal tender but are not intended for circulation. They are targeted at bullion investors or collectors who appreciate the special editions as pieces of art.
This commemorative one kilogram silver coin celebrates one hundred years since the armistice at the end of the First World War. It is the last coin in the First World War Centenary Collection.
The Royal Mint says:
"The centenary of the First World War is one of these occasions, a chance to pay tribute to those who fought in the conflict. In 2014, we embarked on a five-year series of remembrance, taking the nation from the outbreak of war to the Armistice.
The collection comes to a close in 2018, as we look back to 1918 with the final kilo coin in the series. British sculptor Paul Day has created a moving design for the coin’s reverse, reminding us of the human cost of war with the image of a lone soldier. This edition of the coin is struck in a kilo of 999 fine silver, finished to Proof standard - the highest quality used for commemorative coins. Imperial War Museums have worked with us to produce the accompanying booklet, which includes specially sourced images and information, and they will receive a donation from each coin purchased to continue their important work." | 
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