This Bulgaria 1930 10 Leva coin shows "The Madara Horseman", "Krum" in the Cyrillic alphabet, and the date "814". The "horseman" is a rock relief carved into a vertical cliff face depicting a life-size horseman, a lion, and a dog. It is located in northeast Bulgaria. Before World War 2, the common belief was that the horseman was Khan KRUM who ruled Bulgaria from 804 - 815 AD. In fact, a Bulgarian coin was minted in the 1930's with a picture of the relief credited to Khan KRUM. Many investigations later, a leading Bulgarian archaeologist, Vesilin Besheliev, determined the age of the relief at 705 AD, almost 100 years before Khan KRUM. The wrong king got credit on this coin. I guess this makes it an "error coin". Bulgaria also struck this coin in 1943:
Now that is interesting. While I have seen the Madara Horseman on many coins (it is depicted on all current stotinki circulation pieces), I was not aware of this "misattribution" on the earlier pieces. Thanks! Christian