Two German Offsets On Reverse

I would like to share two examples of offset on reverse (German: Abklatsch) from early German material and ask for your opinions, especially regarding the second item.
1. 1868 North German Confederation – 1 Groschen red
It shows a strong and nearly complete mirror-image offset on the reverse.
From what I understand, such full offsets are collectible but not particularly rare on classic issues. I would still be interested in hearing how common strong, full impressions like this are considered on this issue.
2. 30 Pfennig – Deutsches Reich (not officially issued?)
30 Pfennig value in this design was not officially issued and is not listed in the specialized Michel catalogue.
This raises several questions:
Was this value prepared but never officially released?
Are such examples known and documented in specialized literature?
How should such a piece be classified — unissued essay, proof, waste, or something else?
I would very much appreciate the opinions of specialists in early Deutsches Reich material regarding the status and classification of this 30 Pfennig stamp.

Your 30pf looks like postal stationery. (Maybe they both do...I haven't looked at the 1g.) As one example, 30pf paid the freight for a pneumatic envelope in Berlin:




[Please don't pick at die differences, if any; this is just a suggestion.]

cjd - Thanks, I think you are right. I guess the printing process of postal stationery was similar: sheets were printed, stacked, dried, then processed further. If stacked before drying, set-off could occur exactly the same way.

Maybe? Stacked set-offs aren't usually so clear. Consider another possibility, in the case of postal stationery.

A set-off reversed impression can be created when the press cycles without a piece of paper, effectively printing the design on the platen. The next piece of paper through the press picks up that ink from the platen and ends up being printed front and back, at the same time.