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.
Britannia as a symbol - the female personification of Great Britain - has been depicted on British coinage for centuries. The bullion series called Britannia has been issued in gold since 1987 and in silver since 1997; it has a "definitive" depiction - used on bullion coins (Brilliant Uncirculated grade), as well as “Britannia, the Changing Face of Britain” - a series of one-year design used on proofs made for collectors, such as this one.
The Mint says about it:
"Portrayed in a vibrant new design for 2022, Britannia - the noble female warrior who appeared on Roman coins almost 2,000 years ago - continues to inspire a nation.
Since first appearing on coins during Roman times, Britannia has endured as a symbol of strength, hope and progress. Chronicling pivotal moments in the story of a nation, leading engravers of each age have reinterpreted the icon on both coins and medals. In 2022, our young product designer Dan Thorne has created a bold and vibrant icon that celebrates past achievements, whilst looking to the future. His design echoes George William De Saulles’ Britannia, which appeared on the reverse of the florin from 1902 and shows Britannia turning slightly over her shoulder, whilst confidently facing forward. Using innovative digital design methods, Dan has brought a modern and exciting feel to this flagship coin range, appealing to experienced investors and collectors alike." | 
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