Ten shillings

Something wrong here surely? The Scotsman reports:

"Mr Sheridan is conducting his own case in court and, in cross-examination, he put it to Mr Green that the minutes did not accurately record what had been said at the meeting, and were "as dodgy as a ten-bob note"."

There is nothing dodgy about a ten shilling note - they were perfectly normal. The phrase Mr Sheridan must have been seeking is 'dodgy as a nine bob note'.