This set is part of a series designed by John M. Mercanti, who was the 12th Chief Engraver of the United States Mint from 1991 until his retirement in late 2010.
The Royal Mint says about the series:
"Potent symbols of courage, strength and freedom, the British lion and the American eagle characterise the spirit of each nation. Richly historic and instantly recognisable, together they represent the shared values and enduring relationship between two countries that have traditionally stood shoulder to shoulder."
The design was first issued in 2023 in proof grade, and has since been re-issued in a number of formats. The four coins in this set are only available through it, they were not released individually. There is a silver proof ounce (the silver ounce released separately is reverse frosted, unlike the coin in the set), and three fractional sizes: half, quarter and one tenth of an ounce. | 
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