Machine Doubling. This is very common on the 1968-1972 cents. Note the affected area is a reduction of the normal size of the devices. The machine caused this damage after the strike of the coin. Kind of a kick in the shin after the strike. They allways look flat and remove the contour of the coins. Very common. Even happens on doubled dies as well. But a doubled die has the hub doubling on the die and the doubled die will even happen, but the MD will alter the strike slightly. Want to see an example of it?
This is the big DDO of 1969-S. Note the date digits are doubled? Note the yellow arrows. That is where the MD happened after the strike. There are probably more examples of the DDO with MD, than the ones without it. Very common.