The Logic Off Topic list

Hi knowledgeable people of the OT list,
Since this is the OT list, I might as well ask this question: what 
does MINT mean? In the context of when people are 
talking/writing/selling a product they mention that the product is in 
MINT condition.
English is not my native language, so I don't understand this term. 
Can somebody please explain?
TIA,
Yoonchi.