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, then also two kilos (they are actually fractionally heavier as a whole, to account for the small amount of other metal in the alloy).
The 2 kg silver coins are denominated as One Thousand Pounds (£1,000), 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 two kilograms silver proof coin commemorates Prince Philip, Duke of Edinburgh, prince consort of Queen Elizabeth II.
The Royal Mint says about it:
Following the announcement of the passing of His Royal Highness The Prince Philip, Duke of Edinburgh on 9 April 2021, many reflected that his was a life well lived. A man of action and significant achievements, Prince Philip became a naval commander at a young age and provided steadfast counsel to Her Majesty The Queen throughout her reign. When his young wife first took on the role as monarch, the newly titled Duke of Edinburgh supported her, showing tireless dedication to his duty. This exemplary service was recognised by The Queen at the time of their 70th wedding anniversary in 2017, when he was appointed a Knight Grand Cross of the Royal Victorian Order (GCVO). In honour of this remarkable man, The Royal Mint has created a coin to celebrate his life and legacy. The design features a portrait created by Ian Rank-Broadley FRBS that was personally approved by The Duke of Edinburgh in 2008. | 
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