I don't collect plate flaws in Soviet Occupied Germany stamps (SBZ). It's difficult enough for me to collect the regular variations! It can get complicated (and expensive) quickly!
For those of you unfamiliar with SBZ stamps, let me give an example:
The East Saxony stamp that Johan showed, MiNr. 51, has 10 "standard" combinations: Paper differences (3); gumming differences (2); types (2) and paper color (3).
The paper can be:
1. Grey to yellowish, thin paper with a fine net structure (0.07 – 0.105mm)
2. Grey to yellowish, thin paper with sharply climbing laid paper lines (0.075 –0.095mm)
3. Grey to yellowish, thin paper with sharply falling laid paper lines (0.075 – 0.095mm)
My scanning skills are not good enough to provide pictures of these paper types. The usual procedure is to hold the stamp facing you in front of a bright light to look for the paper lines. It can be a real bear if your stamp doesn't have good margins.
There are two gum variations:
1. Smooth or horizontally stripped gum, yellowish to brownish

This type of gum was difficult to scan. The picture is from the Michel Spezial.
2. Economy gumming "Spargummi."
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This is an interesting type of gum. In order to reduce the amount of costly gum on a stamp, a perforated stencil was placed between the paper and the gumming machine. The gum was only transferred at certain points. That explains the "honeycomb" look.
There are two types of stamp:
Type 1 has the top of the numeral three coming to a point and Type2 with a flat topped numeral:

And last but not least there are three paper color variations: black-brown, pale grey-brown and (brown) black. The differences are subtle and don't show up on a scan. It is customary to get a BPP certification to distinguish these colors.
This just touches the different variations found on SBZ stamps. There are other color, gum, paper, watermark and perforation variations on other SBZ stamps.
These differences don't address the hundreds of plate flaws. In fact, the Michel Spezial says: "More even than the other East Saxony stamps, MiNr. 51-52 have such a great number of genuine plate flaws that a complete cataloging would exceed the scope of even a specialized catalog."
If you like flyspecking, these stamps are for you!
Dan
