AAA: Mint: as issued.
AAA: Excellent: clean front, clean back, edges and corners are clean, about as issued.
AAB: Very good: clean front, back may have glue traces, no dirty or rounded edges or corners, no creases.
BBB: Good: Slightly soiled on back or front, possibly slightly dirty or rounded edges, slightly mounting damage on the back.
CC?: Poor: Anything worse than good. Normally a strong crease or important mounting damage on the back.
AD?: Slightly trimmed: part of the edges are cut.
AE?: Trimmed: edges cut, down to the image border
Code: 1° Front; 2° Form; 3° Back
A: 1° clean front; 2° edges and corners are clean; 3° clean back
B: 1° not 100% clean front; 2° slightly rounded edges; 3° glue traces, very slightly mounting damage
C: 1° slightly dirty; 2° rounded edges; 3° slightly creased or slightly mounting damage
D: 1° dirty; 2° slightly trimmed (part of the edges); 3° mounting damage or creases
E: 1° slightly damage; trimmed; important mounting damage
Exampel: ABB: clean front; slightly rounded edges; glue traces or very slightly mounting damage.