The 1969 edition of “THE CLASSIFICATION AND VALUE OF ERRORS ON THE LINCOLN CENT” by Jean Cohen The WEB!!!
CPG,a library of reference books, Web sites, and even here to see if anyone has posted a find before. Flying Eagle and Indian cent die varieties The best of Jefferson nickel doubled die varieties Breen encyclopedia Valentine on half dimes Guide to misplaced dates by Flynn Guide to three cent pieces by Flynn Guide to omm by Flynn Encyclopedia of world gold coins Guide to half dimes by Flynn The Red book plus other books, magazines, on hand.
I am surprised no one mentioned Variety Vista and CONECA...I think that the e-books and the Master Listings there are one of the best resources out there. http://www.varietyvista.com/ Larry Nienaber
Strike It Rich Cherrypicker's Guides Valentine on half dimes Variety Vista and CONECA Vamworld Various websites
At a coin show I look at coins, I look for things like overdates, repunched dates, over mint marks, repunched mint marks, heavy clashes, heavy die cracks, cuds.... If a coin is not called out as such and priced based on condition, I buy it. Once I get it back to my Numis-Lair that's when the books enter into the picture. I probably have over 100 books in my arsenal, some day I'll catalog them. I have to say the most used books in my library are Kevin Flynn's, his photos are by far the most helpful.