Inverted center pieces on stamps became a concept when two-color stamps began to be printed. The printing technique was then more primitive and took place in two separate processes. First one color was printed and then the next. This created the possibility that the middle piece could be printed in reverse. The best known and most expensive example of an inverted centerpiece is the “Inverted Jenny” from the United States. You can read about this stamp it in my blog at stampstars.com. Today’s stamp is from the Dominican Republic and has an inverted center. It is issued in 1902 and is rather common with a value of around 20$.