> The registration of a trade mark may be cancelled if another person has acquired rights to a trade mark prior to the date that is relevant for the seniority of the registered trade mark within the meaning of section 4 no. 2 or to a commercial designation within the meaning of section 5 and these entitle him to prohibit the use of the registered trade mark in the entire territory of the Federal Republic of Germany.
Where the cited section 4 no. 2 is
> The following shall give rise to trade mark protection: [...] the use of a sign in trade in so far as the sign has acquired public recognition as a trade mark within the affected trade circles
You might try to go this route via a court-case, while the chances in our case with prior use and trade show appearance was evident were rated as very bad by our lawyers, but again, this is usually out of scope for the resource options of a startup/small business.
1. The mark has to be used in a commercial setting
2. The mark has to enjoy a reputation within that sector of the market
3. The mark has to have distinctive character
Problematic is usually the second one. It is interpreted by the Federal Supreme Court that (bearing exceptional circumstances) at least 50% of participants in the market have to recognize the mark. The more generic the mark is, the higher the threshold.