Like many other mints, the Royal Mint issues bullion coins in precious metals, having much higher intrinsic value than their face value. The five ounce (5 oz) silver coins are denominated as ten pounds (£10).
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. The coins are typically "one-year" types usually issued in parallel with smaller denominations with the same reverse designs.
This silver five-ounce coin denominated as £10 is part of the Tower of London Collection coin series by the Royal Mint.
The Royal Mint says:
Starting with The Legend of the Ravens, the collection continues in 2019 with coins featuring The Crown Jewels, Yeoman Warders and The Ceremony of the Keys. Together the coins tell the story of this mighty stone fortress and the ancient ceremonies that still take place within these walls.
History comes alive at the Tower of the London. From Traitors’ Gate to the Bloody Tower, within its stone walls echoes of the past are everywhere. Once home to kings and queens, lions and bears, its most famous residents are the ravens.
From the Crown Jewels to the iconic Beefeaters, the Tower of London gives millions of visitors each year the chance to experience living history. However, not all will witness the intriguing Ceremony of the Keys, the ceremonial locking of the Tower gates - which is the oldest military ceremony in the world. Two vital parts of the ceremony, the keys and lamp, feature in the design of the coin.
The formal locking and unlocking of the Tower gates started in the mid 1300s, on the orders of a furious Edward III. The King turned up unannounced at the Tower one night in December 1340 and walked straight in, unchallenged! After imprisoning the Constable of the Tower, Edward de la Beche, for dereliction of duty, Edward decreed that the castle should be locked at sunset and unlocked at sunrise.
At exactly 9.53 pm every day, the Chief Yeoman Warder, dressed in Tudor watch-coat and bonnet, and carrying a candle lantern donated by the Honourable Artillery Company in 1919, leaves the Byward Tower and falls in with the Escort to the Keys, a military escort made up of armed members of the Tower of London Guard. The Warder passes his lantern to a soldier, and marches with his escort to the outer gate of the fortress. The sentries on duty salute the Queen’s Keys as they pass. | 
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