old money
nounBrE BrE//ˌəʊld ˈmʌni//; NAmE NAmE//ˌoʊld ˈmʌni//
[uncountable]used to give an amount, a measurement, etc. using older or more traditional units that may be more familiar to some people The fish measured 29 centimetres (that's a foot in old money).
Check pronunciation: old money