That is Machine Doubling. These devices are incuse and Machine Doubling enlarges these devices. On the raised devices Machine Doubling reduces the size of the devices. These devices are not raised. Do you know where the DDR's are on these reverse designs. In the central area of the designs. I did a test on 100 random quarters and found out that 70% of the ATB Quarters with the incuse devices had some form of Machine Doubling. Anywhere from slight/mild/med/large Machine Doubling. only 30 of the 100 didn't have Machine Doubling. This is very common to find. There has not been a true DDR on those devices reported and I doubt that there will be. Because on incuse devices, the devices are made smaller on doubled dies. Here is an example on a 2013 cent:
But the location of these devices do not show any reduction be the hub doubling only on the central devices on incuse devices. On the raised devices on the central area, they can be found. I just checked none have been attributed on the reverse for the raised devices yet.
Well they have used the incuse designs at different times. The most common is the VDB on the 1918-2020 cents. The 1918-1934 were actually V.D.B. After 1935 the dots don't show on them any longer. When the dies are over polished, the incuse devices because they are raised, can be polished off.
There were some quarters with it on the states quarters. On the Buffalo nickels and the Standing Liberty quarters, if they had used incuse devices, the dates would still be on the coins today. But I'm not familiar of a list on incuse devices anywhere.