"S" over "D"

The San Francisco Mint produced a major Overpunched Mintmark (OMM) error on the 1946 S Lincoln Wheat Cent (Penny). The best way to identify this error is to note the "S" mintmark stamped on top of a subtle "D" mint mark (S/D OMM). The location of the "D" is depicted by the arrows in the example image where it is subtly seen within but under the "S" mintmark.