Isle of Man nobles are equal to 10 pounds...

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TYNWALD COURT, 12th JULY, 1983

The design of the Noble shows on the reverse a facing view of a Viking longship under full sail and the inscription "1 oz. platinum fine" and "One Noble". The obverse is the familiar Arnold Machin effigy of Her Majesty the Queen and the inscription "Isle of Man Elizabeth II" and the year of issue. The Noble will have a face value of £10 although, in common with Manx and other gold coins, this will not be stated on the coin itself. Of course this face value of £10, the legal tender value, is nominal in relation to the value of its platinum content, which at today's prices will be somewhere round about £270.

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Looks like the original idea was for 'Platinum' Nobles to have a face value of £10, subsequently amended for Silver, Gold (and other metals), but the legal tender value has remained at 1 Noble = £10.

tynwald.org.im you can find information on the angel, and the platina as well...