I was sorting through my pennies, when I came across this 1976 dime. It has no mint mark, and all of the markings on it are pretty normal. On the reverse where it says, "E-PLU RIB USU NUM, the letters USU look like OSA, only the "A" looks upside down. Also, there are traces of copper plating on the coin. At first I thought it was rust, but it's definitely copper. It has some surface scratches, so maybe the copper got scratched onto the coin? It's probably nothing, but thought I'd check here before I put it into my change jar. Thanks
Until roughly the mid 1980s a popular cleaning method for dug non-premium clad coins and pennies was salt and vinegar. It knocked off most of the crud and allowed the coins to be spent. If folks did not keep the clad separate from the pennies the end result looked like this. Another "cleaning" method was to carry your clad in your pocket for a few months. That technique resulted in a cameo appearance with the field solid dark and the raised portions looking like a normal circulated coin. Easy to spot when found in circulation.
Thank you Harley, This is great, it helps a lot to know how to spot these types of things. I appreciate your insight.
A sub category of collecting are those folks attempting to complete matched sets of "black" buffalos. I have folders for everything and am trying to complete an entire US dug set. My "fillers" are holed and cull coins. I have noticed that ground chemicals and composition create different colored coins. In my buffalo set I have red, brown, blue, green and black coins in solid colors. Black silver coins come from fresh water with lots of hydrogen sulfide from rotting leaves and vegetation. From the ground most silver is bright and clean. You see lots of stuff come out of the ground and water. Makes for a cheap challenging set even if only a type set.