Most of  the products of Krause Papierwerke come very close to originals. Some are virtually indistinguishable by casual collectors, which creates a risk of my products being sold by dishonest traders as originals. Especially after some minor effort aging them. 
As forgeries of German WW2 items is a real plague these days, I felt the need to add some level of protection against such practice. Since March 2018 all Krause Papierwerke products that could pass for an original have been marked as reproductions with a big round "invisible ink" stamp that can be only seen under black light. It is not visible under normal light conditions and does not interfere with authentic look and feel of a document. However anyone in possession of inexpensive UV light (available on ebay from ~$5) will be able to identify Krause Papierwerke product. 
This will not completely prevent the chance of misuse, but will give potentially cheated buyer an opportunity to demand refund.
Below you can see what to expect - the same 2 products in visible light and under UV.
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Other hints for collectors who'd like to confirm authenticity of their documents:

• Smell your document - practically all 80 years old documents do have a specific, old smell to them. If there's no smell at all, or it smells like chemicals, that's a warning sign. That's especially true of books. 

• Paper yellowing - most single sheet documents (not books) show more yellowing on the edges than in the center

• Paper fragility - this one is tricky, as you don't want to damage your original - the paper of documents from WW2 era is fragile. Even the ones printed on cardstock (thick paper) feel a bit "dry" and fragile. If your document's paper feels like modern copy paper or cardstock (which are very hard to tear or break), there's a chance it may be younger than advertised.

• Check with Krause - I'm happy to help you determine if there's a chance your document is a fake. Just send me a message and attach the photo of the document in question. Over the years, looking at thousands of documents, I developed instinct that quickly identifies if something's fishy about a document. I'll be happy to help!

Oberst Krause.​