As queer as a nine bob note

A bob is slang term for a shilling, part of British currency before decimalisation. Of course, nine bob notes never existed. As shillings came in ones, twos and tens, a nine-bob note would be a forgery, and therefore very bent indeed.

The date of the phrase's coinage isn't known, but the American version 'as queer as a nine-dollar bill' dates from at least 1965, when it was included in John Trimble's 5000 Adult Sex Words and Phrases:

Nine-dollar Bill... An Absolute Invert or Homosexual. From the inference that one is "Three times as queer as a three-dollar bill".

In the UK, until 1971, when they ceased to be legal tender, the brown ten shilling notes were a commonplace. They were popularly called a 'ten bob note' or 'half-a-nicker' (a nicker was a pound).

The British version had variants; for example, 'as queer as a nine-bob watch', which would be suspect on account of its unrealistic cheapness