Several months ago, I tried to identify these stamps.
Unfortunately I didn't find it.
I try to explain with pictures with stamps how you can identify valuable stamps (Michel ed.2011) I do not know German so I can make mistakes in my explanations.
For sorting it was easier for me to use print types (See Fig 1). Scott # O1-O17 litho print.After, only typo print.
Litho print in two emissions (See Fig.2):
-first emission (with 3 lines of points) originals
-second emission ("nachdruck" term in Michel-with 5 lines of points and only CTO) They have a very small value except the values of 12.15,16 and 70 pfennig which can be found without CTO (300 Euro)
Follow the typo print emission (See Fig 1) with different papers, watermarks and perforations.
Michel's page with valuable stamps - See Fig. 6.
The conditions to be met are:
-granite paper (See Fig 4-textile fibers in composition)
- type I or II stamp (See Fig 3) I saw in a preview post a change in Michel ed.2019?
- 2XI or 2XII watermark (See Fig 5) - I failed to distinguish them on my stamps (watermark 297 in Scott)
If you have watermark 3X (Scott 313) the stamp is a low value (See Fig 7)