An extremely rare 1937 proof gold sovereign featuring the profile of controversial British King Edward VIII was recently sold at a Baldwin's auction in London, fetching a world record price for a coin struck by Britain's Royal Mint. The hammer price was £516,000 ($874,310).
The Edward VIII sovereign did not go into production due to Edward giving up the throne to marry a twice-divorced American woman, Wallis Simpson. This 1937 gold sovereign is one of only two known to exist. The only other example is in the only known complete proof gold set of 1937 Edward VIII coins.
Complete description at Baldwin's.