I told you earlier about the X-factor (perforations), the Y-factor (margins or centering), and now the final and maybe most interesting Z-factor...
For unused stamps we will use it to give a qualification to the gum, for (postally) used stamps, the quality of the cancel.
Let's first talk about unused (MNH) stamps
"5" MNH means Mint, never hinged. *** or ** in catalogues
stamps have the original gum, no spots, no mark of any kind (except an expert's mark - for professionals)
"4" MLH menas Mint, lightly hinged. * in catalogues
The original hinge was removed or a small part remains on the stamp, furtheron no defects to the gum, no spots
"3" MH, Mint and hinged.
The hinge mark is still visible, or is removed but a larger part of the stamp is affected
|X Y 5 X Y 4 X Y 3|
"1" Mint (unused) less then 50% of the original gum is left on the stamp
"0" MNG (mint no gum) (*) in catalogues
Unused stamps, but no (original) gum left - can be a used stamp without any cancel
|X Y 2 X Y 1 X Y 0|