1971 D Lincoln Cent Double Die?

The devices are smaller because of die polishing. But on the outside edges of devices where we always see Machine Doubling, that is what you are seeing. On a doubled die you will see the devices showing spread in the centers. That is what to look for on a doubled die.

But your coin is not a doubled die. The outside edges are affected but the centers of the devices are not enlarged like you would see on a doubled die.