If something that is not new is in mint condition it is perfect and as good as new.
This expression has its origins in the new coins produced at the Royal Mint; where UK coins are made and distributed.
Exampes of use:
1. My copy of Charles Dickens’ book Oliver Twist is in mint condition.
2. Her 1937 Buick is in mint condition.
3. He has a collection of mint condition Batman comics.
Image © Don O’Brien