10 - This is as good as it gets, probably an SP master on a high quality tape.
9 - Still EX, probably an LP, EP master on a standard grade tape.
8 - Great quality. Most likely a first generation copy.
7 - Good quality, first or second generation.
6 - Decent quality, shows sign of ageing, maybe some jitter.
5 - Not very good quality, tracking problems, jitter, color bleeding.
I won't even list it if its below a 5.