A lot of new collectors take a while to figure this out. The biggest clue: They are flat, shelf like, ruding the over all size of the device. If it were hub doubling, then it would be raised and enlarged as the doubling is on the die. The flat look comes from die movement after the strike that alter the devices.
Doubled dies that are enlarged in 3-D:

Do you see the enlarging of the device?

This may look like MD, but note it is rounded and not flat and shelf like.

On MD coins, we often see this showing one color as they are flat. But note on this coin the contour of the area affected show a light to dark area as it is rounded.


So we can see that the devices are raised on doubled dies and rounded. This happens because the hub doubling is on the die. Each coin will show the same doubling.
RPMs that show the enlarging in 3-D:


Can you see that the RPM is raised above the field and is not flat or shelf like?


On this one you can see the die flow over the raised area. That show that this has been on the die for some time, but is still there. If this were an issue with MD, then that area would be flat and also affected the normal shape of the mint mark, not the field.



Note again it rises from the field. If this were MD, then it would affected the mint mark. The RPM is separate from the mint mark.


This RPM is very close in spread, but not how it enlarged the mint marks and shows two distinct mint marks on top of the other one?
Machine damage that reduces the size of the devices in 3-D

Note how the devices are reduced from the machine damage after the strike?
Hope this helps a bit more?