Beagle,
You will remember the days of travelling to Italy before the Euro; and justifying the expenditure you incurred unwittingly (in a currency where even children were millionaires) and nobody had any change.
It got so bad under one OC Accounts that OC "XX" Sqn did the next trip to Rome and returned his Imprest to the Plt Off Accountant together with a large bag of boiled sweets; patiently explaining that "the orange ones are 20 lira; the green ones are 30 lira, the red ones are 50 lira" etc.
Then there was trying to explain that you really needed US Dollars and UK Pounds to go to Moscow; they didn't want roubles - they had enough of their own.
We once took an OC Accounts as imprest holder on a training flight - never, ever, again. It took months to sort out the paperwork!!!