An applicant sought to register the "smell of candied almonds" (gebrannte Mandeln) for jewellery and watches in class 14. The Swiss IPO refused, noting that a description of a smell is insufficiently clear (with reference to ECJ C-273/00, Sieckmann). The applicant then amended the application and included a detailed recipe, specifying the type, quality and quantity of each ingredient and giving step-by-step instructions as to how to prepare candied almonds. He defined the trade mark as the smell at the end of the cooking process in a 12 sqm kitchen with tiled floor and stainless steel plumbing, window closed, no ventilation. 

Both the IPO and the Federal Administrative Court held that the smell was still insufficiently defined, because temperatures in the pan could vary, mineral traces in the water might change the smell, and the skill of the cook was a subjective element that could not be standardized.

The gist for the practitioner is: we don't want no stinking smell marks. Because repeated insistence that "there is no known method for describing a smell graphically" do not change the fact that a well-specified cooking recipe with so few ingredients (almonds, water, sugar, vanilla extract, cinnamon) and a well-known process (caramelization) will result in a smell that is, for all practical purposes, consistent. After all, any depiction of a trade mark is an abstraction, whether it be a word mark, shape mark, colour mark or any other type of mark.

Link to summary of decision (in German, with link to full text). The decision could be appealed to the Supreme Court, but I don't expect it to be.