The DD214 is THE document you need when you retire or separate. It gives dates of service, character of service, type of discharge, medals and awards earned, etc. The DD217N is a “warm fuzzy” document that you frame and hang on the wall so everyone can see you done good. It is is along the same lines as a diploma from high school, easy to fake. I would never accept a DD217N as proof as service as it is too easy to fake.
The DD214 is a Certificate of Release or Discharge from Active Duty, and shows among other things the type of discharge that was given. This certificate is used as proof of military service to receive veteran benefits or to claim veteran hiring preference.
The DD217N is a Certificate of Service showing that someone served in the Navy. This certificate is hung on a “I Love me” wall and looks pretty. <https://www.flickr.com/photos/lids3qy/11714361364%…
4 and 7N