Some Navy terminology...
-"Identification Badges" are devices worn for serving in particular billets (i.e. Presidential, Vice Presidential, OSD, JCS, Combatant Command, Law Enforcement/Master-at-Arms).
-"Breast Insignia" includes Command-at-Sea, Command Ashore, Program Manager, Warfare Qualifications (i.e. SWO, Wings, Dolphins, SEAL, EOD, Craftmaster, Supply, Merchant Marine, etc.). These come in "large" (wear on working, service, and dress uniforms) and "miniature" (wear on dinner dress uniforms) sizes.
-"Awards" are normally comprised of medals and ribbons (at LITS explained). As applicable, Sailors have the option of wearing only their senior 3 ribbons or senior 5 medals. Therefore, just because a Sailor wears only 3 ribbons, isn't indicative of all of their awards/decorations -- this is more common with senior and flag officers. As for non-prior plebes, if they are only wearing 3, it is probably because they only have 3.
USNA has been awarded the MUC twice: Aug 96 - May 98 (primarily Classes of 1997, 1998, 1999, 2000, 2001) and June 07 - Aug 08 (primarily Classes of 2008, 2009, 2010, 2011, 2012)