When we were in Los Angeles a few years ago, we were quite surprised to discover a pair of motorcycles in the hotel parking lot with Swiss plates. It turned out to be two mates from Lucerne who had imported their bikes to California for a month long tour. One had a vignette on the upper front fork. As I didn't see a vignette on the second bike, I inquired after it & was told that it was indeed affixed under the seat as the rider didn't want to damage the paintwork.

The question that occurred to me was how often would you be pulled over in Switzerland if you did the reverse? Not the vignette, but rather how often you might be stopped by police if you drove a bike (or car) in Switzerland with plates from another continent? Probably ridiculously often. r