Both coins were struck from the same obverse die. Lighting was changed for the close up shots to show more clearly the small dots. The small raised dot between the noses was a feature of the die indicating the center of the field. It probably served as a center point for a compass used to lay out the border of dots. The right coin shows a prominent centration 'pit' on the right face (Tranquillina). The equivalent pit on the left coin is much weaker but destroyed the bridge of Gordian's nose and can be seen just left of his eye. This pit shows rotation with slightly raised ridges suggesting that whatever made the pit rotated while the one on the other coin did not. Since the pits are not in the same place, they were not a feature of the die but were from flan preparation. Since many (most?) of the recessed pits show no rotation, I suspect that a tool was used to surface the flan which rotated around a central hub that was supposed to remain fixed. When the tool jammed from shavings or dirt, the center point could break free and rotate with the tool producing the rounder form of pit with ridges.