1952 D Errors Side By Side Comparison!!

It appears to me that the D MM's are different sizes and in slightly different positions.

1952D Comparison MM Positions

Mint marks were added to the dies by hand until 1989 so slight positional variation is to be expected. The date on the second coin has several contact marks, most notably on the top of the 5 and 2. I see two perfectly normal coins.

The 1952-D cents had three different mint mark styles:
http://www.varietyvista.com/01a%20L...20Styles.htm
The MMS-003-005 could be found. (yours appear to be the same styles but hard to tell with the images provided) None are preferred more over the others. (that I know of. yours look like MMS-003) Circulation flattening makes them harder to tell from you images. The locations vary because they were hand punched onto the dies. Location/rotation/serifs make the dies often to look unique. They are handy for Identifying varieties for them. Helpful for RPMs and doubled dies both to match an attributed die if they are present on a coin.