Germany Allied Occupation Stamps With Image Visible On Back Side

I have three stamps ("Numerals") with image also visible on back side. Please look at two attached scans showing those 3 stamps side-by-side with identical normal stamps. Image on back side is very bright, specifically on 2pf stamp. At the same time gum is undisturbed and paper thickness is normal (so issue is not related to paper transparency).
I am sure that somebody can help with right term for this type of errors so I can start research. Google did not help me so far...
Thanks

Hello, Look under the word Offset(English) or abklatsch(German). This is what you got. Kind regards, Johan.

In English it is now called setoff in order to differentiate it from offset, which is a printing method.

Peter

Peter - thanks! "Setoff" is a key here. I found some discussions about this issue, but still not sure how this image is imprinted on the back of the stamp - just by physical contact with another sheet of stamps?
Though it seems that there is not much value in those stamps.

Value depends on the country. In Latvian stamp collecting offset stamps are worth more than the normal printing.

Hello igopp,

I was looking around and found your thread. They are exactly "Abklatsch". For the "Ziffernserie" the value is around 3-5 Euros range MNH. They exist inverted and they are valued at 10-60 Euros range MNH.

One book that you need for the basic if you collect them, is Mr. Hohmann Band 1 (Volume one) It covers the entire series from (Michel) 911 to 970 including booklet and miniature sheet.

Best regards

Hornet

Hornet - thanks a lot. I will try to find any possible links to this book, however my first search on Google did not show anything.
Do you have any additional information (for example title of this book)?

Hi igopp,

Jan Hohmann, Band 1: Marken und deren Besonderheiten

Edition 2009, Hardcover in color.

Volume 1 to 4 exist but for the basic "band 1" is the one to have.

Best regards

Hornet