Re: Pardon vs. Commutation
After having thought this over it occured to me that if a presidential pardon was issued the person pardoned would have been given a document to that effect so that the person could easily show his conviction had been overturned.Also, the person's dishonorable discharge might have reverted to honorable making the person eligable forveteran's benefits. The VA has it's own records on those that apply.
Another, and more probable scenario, was that the person had his sentence commuted. This just means that the president shortened the sentence to time served and the conviction stands.
This could have been done by "presidential directive". The PD would just order the commandants of military stockades to release certain classes of prisoners and there would be no civilian records naming those that were let go.