Take the time to read through the following sites. They provide some in depth information not only doubled dies, but how to recognize worthless things like mechanical doubling and die deterioration, along with info on how coins are made (which will also help you determine mint errors from post mint damage). http://www.error-ref.com/ http://doubleddie.com/58222.html http://www.varietyvista.com/ Lots of stuff here and you're not going to pick it all up at once, but it's a good start to learn how to identify error coins
