This is a very tough question to answer and is very subjective, what one person considers to be in mint condition may not be what the next person thinks, but as a guide you should consider the following labels :
MINT – Model is in the same condition as it was when it left the factory, this would be hard to achieve on older models
NEAR MINT – One or two tiny chips or box rubs, visible only on very close inspection.
VERY GOOD – Several small chips, scratches, or box rubs, visible on inspection.
GOOD – Several large chips or scratches, highly visible on inspection. Playwear highly evident.
POOR – Most paint missing. Has missing or broken features (Hitch, luggage, tires, etc.). May have been painted by sloppy “budding junior artist”.