They are not clogged dies. When a Die gets clogged with grease, then the device is not formed. In this case part of the field of the die has chipped away. Thus that area is not formed like normal, but appears as a raised area on all coins struck after this event happens. These are common on the 1950's wheat cents as they over used the dies. So we see this often on this series. It happens other years as well, but not as often as the 1950's wheat cents. Being this is die breakdown, there are thousands of these. So it is not a premium coin. Just coins of a die that was over used.