My dad’s coffee mug has (in addition to an amusing cartoon – if you’re on Communications) his name, silver ‘railroad tracks’ (Lieutenant bars), and ‘N-52’.
He told me once what it meant, but it was so long ago that my memory may no longer be accurate.
What does ‘N-52’ mean?
Hm. The board changed the title from USN to Usn.
What did your dad do in the navy and what era was he in? Doesn’t sound like any designator I am familiar with in aviation.
mrAru says it isnt a boat number, boat designators tend to have 2 letters or 3 letters
[eg - NR-1, the tiny exploratory nuke baby sub, or SSN-21, Sea Wolf {also called Building 21} or CGN-45 Ronald Regan]
It could be a building, or a division at a shore emplacement. It might also be a prototype designator/number if he was a nuke.
N-52 might be one of the VLF sites if he was in communications…was he stationed in Norfolk VA? He thinks that is the designator of the unit just south of Norfolk.
I’m pretty sure he said that the ‘N’ meant ‘Communications’. (He was the Communications officer on the 7th Fleet’s flagship CLG-5 USS Oklahoma City.) I think he said that the ‘5’ meant that he was fifth in command. (i.e., by the time it got to him the ship was probably sinking. 
) I don’t remember what he said the ‘2’ meant.
The only thing I’m fairly sure about is the ‘N’.
FWIW, this was in the 1960s.
Simulpost! Although he worked in the Pentagon for a short time, his service was basically all in the Pacific. (Combat Aircrew on USS Philppine Sea in Korea, USS Lexington on her first cruise after she got the angled deck, radar intercept guy in a Lockheed Super Constellation after that, OCS in '56, Communications Officer on Oklahoma City during Viet Nam, FLEASWTRACENPAC ASW instructor before he retired.)
I’ve actually worked in an N52 shop in a previous job in the Navy. I’m guessing your dad’s mug refers to a staff code. Naval staffs (for commands and large groups) have codes, e.g., typically N1 is Admin, N2 is Intel, N3 is Operations, N4 is Supply, N5 is Plans, N6 is Comms, N7 is Training. This may vary from command to command, but generally, I’ve seen that it’s pretty consistent. Joint commands like the Pentagon or unified combatant commands (e.g., CENTCOM) have similar “J” codes like J3 (Ops).
For large commands, there will be sub codes, like J32, where the “2” might be future ops whereas the J31 may be current ops. If your dad’s mug does refer to a staffing code, I’m not sure what his code would be referring to-- probably the plans dept (the 5 code) and some subset like special plans. Anyway, that’s my guess.
Was he a bingo player?