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
Example: ABB: clean front; slightly rounded edges; glue traces or very slightly mounting damage.