Rating Sytem for Used CD's

Is there a standard for rating used CD's? Can anyone point me to a URL? Do I need to examine and describe the condition of each one...I have about 200 I'm selling and obviously would rather just compile a simple list and use a number rating system. I'm not talking collectible stuff - just your run-of-the-mill redbook stuff. The A'gon system doesn't give a standard for this.

Thanks for any input.

Marco