The C-10 method is the simplest and most commonly recognized by collectors.
It rates toys on a scale designated by C1 to C10.
Assigning a rank of C-1 to a toy represents the poorest condition, while C-10 represents the best condition.
C-10 represents Mint in the box.
C-9 is a toy that would be almost Mint, i.e. like new but out of the package.
C-8: Very clean with minor wear.
C-7 Played with and no missing parts
C-6: Played with but in good enough condition to include in a collection.
(A toy in C-6 to C-7 condition typically rates 60+% of Mint value.)
C-5 and under: 'Give them to the kids to play with'.
Toys in lower grades (C-4 to C-1) typically have paint damage; missing parts; dents, cracks; tears; missing decals, wheels, etc. - as such are sometimes kept as parts toys or just because you like it. Unless toys in these lower conditions are extremely rare, they have little collector value.