1981-D Penny D In D ?

Not an error. That's Post Strike Damage ( PSD) on the mintmark. The mintmark took a hit and it caused the metal to get pushed over and flattened.

You must be thinking of an RPM. You don't have a RPM (RePunched Mintmark) since there's no spread or enlargement of the mintmark. Here's what RPM's are supposed to look like. http://doubleddie.com/310201.html

The difference between a damaged area and a RPM is this:
1. A damaged area leaves an incuse mark on the top of the device.
See example above. Note how the mark is incuse into the coin. A RPM would be raised over the fields.


2. A RPM will have roundness that is raised above the fields.



3. Machine doubled mint marks will be affected by damaging the edges of the devices pushed sometimes in two directions and also be an incuse mark.



4. A damaged punch will leave a raised area on the coin, but because the punch is bent, the affected area will not look like the design of the punch.

5. Die wear on the mint mark will make a beeline more towards the closest rim.

Note how this mint mark direction moves the East edge towards the rim. Just die wear. Not a RPM developing. RPM are created on the die by the puncheon. Not from die wear or damage to a coin.

RPM vs damaged punch on 1979-D cents:


A lot more image I could post, But I think this should cover it. If not ask another question. (I have 9,339 images on my site. finding the right one can be hard to find sometimes.