If you have an eye for this sort of thing, there's plenty of undiscovered treasure to be found Just taking pennies, for instance: 1946, 1940, 1926, 1922, 1916, 1915, 1913, 1911, 1909, 1908, 1903 and 1902 all have scarcer varieties at varying levels of obviousness. If you have a stack of 1921s, see if you can sort them into Obv 2 and Obv 3. There are roughly similar numbers of each.