The older mark AIR-FLOW was registered and used for instruments for polishing teeth aimed at dentists
, i.e., the professional market. Philips, on the other hand, registered and used its younger AIR FLOSS mark for electric tooth "brushes" (cleaning instruments
, really, as they use a stream of air and water) aimed at the consumer market. The proprietor of the AIR-FLOW mark opposed Philips' AIR FLOSS application and failed.
The proprietor of the older mark tried to show that its mark had acquired distinctiveness ("erhöhte Verkehrsgeltung") among Swiss dentists (that may have been pointless anyway, because of the different consumers for the products of the two marks, but bear with me). It could show that it had used the mark for over 10 years, and sold about 2,000 of its instruments in Switzerland - with only 4,000 dental offices in the country, which at least indicates that close to 50% of all dental offices use the products (the court did point out that some of the instruments could have been exported). However, the court noted that none of the brochures, advertising material, and invoices produced showed the perception of the relevant consumers of the sign AIR-FLOW.
This reasoning strikes me as strange. Of course the perception of the consumer is the relevant enquiry. But short of questioning the relevant consumers - i.e., conducting a survey - no evidence on acquired distinctiveness will ever show the perception of the consumer. But advertising expenditures, market share, revenue etc will allow inferences on the perception, no? That seems the point of the exercise, and the court has so far always stressed that while consumer surveys may be the best way to prove consumer perception of a sign, they are by no means the only way. If it dismisses all evidence of advertising, market share and so forth with the argument that it cannot show consumer perception, than trade mark owners have no other choice than to commission a (often expensive) consumer survey.
As for the outcome, rather predictably and in view of the weak signs and the different users of the products probably not incorrectly, the Federal Administrative Court, like the IPO before it, found no likelihood of confusion and dismissed the opposition.
Link to summary of decision of 2 December 2013 (in German).