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American Numismatic Association – The leading organization for coin collectors. http://www.money.org/
ANACS – One of the two third party grading companies who use MADdieclashes and trail dies number system on their encapsulations. http://www.anacs.com/
Collectors Universe Forum – All sorts of coins are discussed in this forum. http://forums.collectors.com/
CONECA – An organization dedicated to error and varieties. https://conecaonline.org
CONECA Forum – A forum dedicated to error and varieties. https://board.conecaonline.org
Coppercoins – Doubled dies and RPMs of the Lincoln cent series are listed here with colored images. Excellent reference material. http://www.coppercoins.com/
Error Coin Information Exchange – Error and variety coins are posted and discussed in this formatted exchange. http://groups.yahoo.com/group/errorcoininformationexchange/post
Error-ref.com – The go to site for definitions of all error and variety coin. The site uses abundant colored images. http://error-ref.com/
Florida United Numismatists – The organization that holds the greatest coin show on
earth. http://www.funtopics.com/
Fly-in-club – A site dedicated to Flying Eagle and Indian cents. http://www.fly-inclub.org/index.html
Franklin-Lover’s – An excellent site dedicated to Franklin errors and varieties http://www.franklinlover.yolasite.com/
Heritage Auctions – An excellent site for looking at great coins that have been auctioned. Great reference material. http://coins.ha.com/?ic=Tab-Home-041408
Independent Coin Graders – One of the two third party grading companies who use MADdieclashes and trail dies number system on their encapsulations. http://www.icgcoin.com/
Lincoln Cent Forum – The best place to go to discuss Lincoln cent coins. http://www.lincolncentforum.com
MADdieclashes.com – An excellent site dedicated to die clashes from the United States and worldwide. Abundant colored images with denominational overlays are contained in this site. http://maddieclashes.com/index.html
Traildies.com – The only site dedicated to the anomalies called “trails” and “wavy steps.” http://traildies.com/
VAM World – A great site dedicated to errors and varieties found on Morgan and Peace dollars. http://www.vamworld.com/
Variety Vista – A master listing of all found doubled dies and RPMs. James Wiles also lists newly found doubled dies and RPMs on this site. http://varietyvista.com/index.htm