Go to www.doubleddie.com and click on the the tab marked "worthless doubling". This is a good explanation of machine doubling and die deterioration doubling. There are lots and lots of these types of doubled coins out there and they have no added value. Learning to recognize them is a key step in learning about errors and varieties. It takes time. Forums like CT can help, but the more you know, the less time you waste on this stuff and the more time you have to look for real stuff
