In my sudden interest in philatelic, I wanted to find something fun for PPGG. Guess what the result is!
In philately, an invert error occurs when part of a postage stamp is printed upside-down! The Inverted Swan, a 4-pence blue postage issued in 1855 by Western Australia, is the world’s first invert error! I didn’t find any picture, but I guess this is the story behind these coins.