Ok, so we (as a group) are very familiar with Trumpets, Cornets and most brass instruments but have you noticed that pictures are often published back to front? Looking at my modest record collection I notice that Louis Armstrong is playing what looks like a left handed trumpet on a CD called c'set si bon, of course this is just the cover designer not knowing any better. Looking a little further I have a Jazz collection of 3 CDs issued by EMI, all 3 have a back to front Trumpet on the cover. On Miles Davis's CD Trumpet man he is pictured peering at us through the reversed curves of his Trumpet.
Have a look at your collections, let's see how widespread this is.