Thanks for your suggestion, but if I accept quid, I think I should also accept other colloquial terms. And it would be undoable to find and check all slang terms for every currency.
Nice quiz! One suggestion: The US Dollar is used in Cambodia alongside the Cambodian Riel in everyday life. 1 USD equals between 3800 and 4400 Riel, and payments are usually made in USD or a mix of USD and Riel, large amounts are usually even advertised in USD. ATMs in the country only dispense USD, if you want Riel you need to get them as change when paying in USD. Could you add the US Dollar as an additional answer for Cambodia?
Could you except "quid" for Pound Sterling?