The Tower Pound
The mint standard that Henry VIII abolished.
Origin
The English coinage standard from at least the Norman period, kept at the Tower of London, and abolished by Henry VIII in 1526 in favour of troy weight.
The catch
Abolishing it was a devaluation dressed as an administrative reform. The troy pound that replaced it was heavier, so the same nominal pound of silver now yielded more coin, and the Crown pocketed the difference.
The Tower pound of 5,400 grains was the standard by which English coin was struck for four centuries, and its physical master was kept at the Tower mint. Henry VIII’s replacement of it with the troy pound of 5,760 grains sits within a reign notorious for currency debasement, and it should be read in that light. The change also explains why troy weight, a foreign standard from the Champagne fairs, came to govern British bullion.
On the evidence
The Tower pound’s abolition as a disguised devaluation is an interpretation rather than a documented motive. No surviving instrument states it, and the change can equally be read as an administrative alignment with a standard already used for bullion. What is certain is the arithmetic — the troy pound was heavier, and the same nominal pound of silver therefore yielded more coin — and the reign in which it happened. Henry VIII’s later debasements make the reading a reasonable one, but reasonable is as far as it goes.