For a comprehensive explanation of these duties, see:
U.S. Navy Interviewers Classification Guide

1st Lt = Deck Force Officer
AG = Aerographer's Mate
ASW Off = Antisubmarine Warfare Officer
B = Boilermaker
Bkr = Baker
BM = Boatswain's Mate
BT = Boiler Tender
CAPT = Captain
CDR = Commander
CM = Carpenter's Mate
CO = Commanding Officer
CS = Commissaryman
DC = Damage Controlman
DC Off = Damage Control Officer
DK = Disbursing Clerk
EM = Electrician's Mate
EN = Engineman
Eng Off = Engineering Officer
Ens = Ensign
ET = Electronics Technician
ETR = Electronics Technician (Radar)
F = Fireman
FA = Fireman Apprentice
FC = Fire Controlman
FCR = Fire Controlman R - Rangefinder Operator
FN = Fireman
FT = Fire Control Technician
FTG = Fire Control Technician (Gun Fire Control)
GM = Gunner's Mate
GMG = Gunner's Mate (Guns)
HA = Hospital Apprentice
HT = Hull Maintenance Technician
IC = Interior Communications Technician
LCDR = Lieutenant Commander
Ldry = Laundryman
LT - Lieutenant
LTJG = Lieutenant Junior Grade
M = Metalsmith
MM = Machinist's Mate
MoMM = Motor Machinist's Mate
MR = Machinery Repairman
OPS Off = Operations Officer
PhM = Pharmacist's Mate
PN = Personnelman
QM = Quartermaster
RD = Radarman
RdM = Radarman
RM = Radioman
RT = Radio Technician
S = Seaman
SA = Seaman Apprentice
SC = Ship's Cook
SF = Shipfitter
SFP = Shipfitter (Pipefitter)
SH = Ship's Serviceman
SK = Storekeeper
SL =
SM = Signalman
SN = Seaman
SO = Sonarman
SOG = Sonarman (Sonar)
SoM = Sonarman
Sup Off = Suppy Officer
TM = Torpedoman's Mate
W = Warrant Officer
Wea Off = Weapons Officer
Wel = Welder
WT = Water Tender
Y = Yeoman