This weird old postcard from Germany is undated, but seems to be about 100 years old. Weird Vintage dug up some information about the joke.
Apparently this is some fancy wordplay which makes a whole lot more sense when you’re in on the joke. User laurentbelkacem explained “About La Fanfare d'Écublens postcard - Écublens is a little town in Canton Vaud, Switzerland. The name of this town is pronounced in a way that in French sounds exactly, in this sentence, like “La Fanfare des culs blancs”, literaly “White butts brass band”.I'm sure you can come up with more punch lines.