If you want a quick refresher of the major types of doubling–hub, machine and die deterioration–view this video. It will help you identify those types with audio explanations by Michael Bugeja.
Click here for an article on the 5 types of doubling.
Also, Proxiblog has assembled some 50 videos on this site and YouTube. Click the photo below to see them.
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You can find more information about types, varieties, errors, grading, bidding and buying in Coin News Updated: The Essential Guide to Online Bidding. Please consider buying or gifting the work for a friend, as it underwrites this hobbyist blog. Thank you.
