1. On the States and
ATB Quarters there are just certain areas that you will find hub doubling on them because of the ways these dies are created.
2. The areas are towards the center parts of the design. Obverse dies, you will see the
DDO either on the earlobes or the motto. That is the common areas they are found.

Note the example on the left first. Note the devices are reduced by
Machine Doubling. The image on the right is showing what a
DDO could look like. These are created on the dies. But the
Machine Doubling is found in any direction and is caused by the movement of the machine during the strikes.
Earlobes:

Note the affected area. Each is showing a raised area copied by the hub. So
Machine Doubling can/may not, be present. The area will rise above normal area either on the fields or on the earlobe area. If the area is flat on that area, that is
Machine Doubling, not a doubled die.
3.
Machine Doubling can happen on normal dies and doubled dies as well. The MD can look different from strike to strike. It is either a machine doubled normal die, or a machine doubled, doubled doubled die. Without the MD doesn't remove the
DDO /
DDR, but as a collector, a Non machine doubled coin would be more desirable as the MD doesn't confuse the issue.
4. On these quarter designs for
DDR's each die needs to be looked up to see what is listed so far on the designs. Depending on the hub movement, the location can be different on each die number. On
DDR has 176 different
DDR's. So knowing what to look for on these is necessary. They will not be common.
Machine Doubling is common, but know what to look for on the target areas of the devices:


Some designs will not have
DDR's. If there is a flat area on the area that could be on this target area, there might not be a
DDR for that design. Other times the design can be lightly off center of these areas. But that is the target areas to look at for a
DDR. Look up the listings for searching for these. Some area easy, others are harder to find. (or may not be any for that design. Always look to see would could happen, then you can see if it did happen on the coins you have.
First! Looking in the same old locations on different designs of the past can be a waste of time. So get out your maps to get to the destination you are wanting to get to. Save your eyes and know where to look for these.
After creating my response for this year/mint/design
http://doubleddie.com/186322.htmlWexler only has
DDO's listed for this design. No
DDR's yet.
Remember Snipe hunting as kids? They would take city kids to the country and them if they ever had been snipe hunting. Give them a burlap bag and drop them off to find something that they have not even heard about for that time. Later they would go back and pick them up again. Cruel trick. But knowing for sure what to look for can save you a lot of time. On your coin, the MD is seen even on the rim, screaming it is
Machine Doubling. remember my story and know what to look for first, then look.
CoopHome:
Do you know what a doubled die looks like? Why knowing will save you a lot more time. (snipe hunt story)