Numismatic News and Information about recent coin types and varieties released worldwide. Focused mainly on official and legal tender issues.
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you can read a curios article about this kind of error (quite standard, «выкрошка штемпеля» or a buildup of metal on the coin, actually non-interesting error), in russian:http://nnm.me/blogs/Krolchatina/bimy/
In Australia we call them CUDS, where the die has broken, common here.