Looking at it more, the original owner may have attempted to clear up some corrosion settling in on a BU coin by pickling the specimen (note the verdigras and where it cleared up a bit leaving a dark stain). Unfortunately, the coin was too far gone and required a longer dip which damaged the coin (any length of soak would damage the coin). A place holder that you can eventually replace with a coin from the wild (with extensive looking and a bit of luck), or purchased for a few dollars. Good luck on the hunt for a better specimen!