What is a “Quid”?

Bill S. writes: During WW2, my dad was stationed in Australia..He bought a memento and paid 40 Quid for it…What is a “Quid”?

“Quid” is a slang expression for the denomination “pound”. This is analogous to using the word “buck” for a U.S. dollar. Both Australia and England were using the denomination “pound” during WW II.