Thanks for the cited threads. I did not notice them. They do not explicitly discuss counterfeit batteries, however. As I said, a third party battery is not a problem, if it is sold as such. A battery bearing a trademark which is proven to be counterfeit is not the same thing.

In the mean time, I have searched and found that this is not small matter. In Germany, see § 263 StGB, § 14 und §15 MarkenG, up to 5 years prison for the seller, damages to owner of the trademark and destruction of the offending goods. I am fairly certain that your local legislation has the equivalent provisions.

I have contacted Amazon.de and am waiting for an answer before I send the batteries back.

Interested people fluent in German may also read:
http://www.linksandlaw.de/urteil125-waren-haftung.htm
http://www.heise.de/tp/r4/artikel/19/19608/1.html