Mercury dimes or winged liberty dimes were minted between 1916 and 1945. They weigh2.50 grams and have 90 percent silver and 10 percent copper. This coin is very collectible because of the silver it contains. My friend once found a 1937 dime on the sidewalk. Some key dates are 1916 D 1942 over 41 1941 over 42. The 1945 S has a size of the date. If its smaller than regulaur its called. A micro s. And dimes dated 1923D or 1930 D are counterfeits. Though not many are in circulation if you get lucky you could find one. So go hoard those dimes!