
This part of the reverse design on the ATB Quartes is incuse (recessed into the surface of the coin), which leads me to believe it is Machine Doubling.
As explained by Dr. Coop on CoopHome:
"on the ATB Quarters all the devices inside the ring area on the reverse of the quarter will be incuse devices. So any slight movement will affect these devices by enlarging them. But instead of being a doubled die, this is called Machine Doubling. I did a test of 100 random quarters I found in change and 70% of them had slight MD or strong Machine Doubling on them. Only 30% were normal. So it is no wonder new ones find these and think and sell them as doubled dies. But they are machine doubled examples."
Reference: https://goccf.com/t/313322