Naval History and Heritage Command

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Navy Numbers

--O--

Note: Where the same abbreviation has more than one meaning, the several meanings have been arranged alphabetically. Abbreviations preceded by an asterisk (*), other than Navy numbers, may never be used singly; those preceded by the symbol for number (#) are the Bureau of Personnel Condensation Code for use in dispatch orders to personnel.

O -- First letter in the Navy aircraft designation, indicating an observation plane

 O -- Horizontal Opposed (aircraft engine)

 O -- Lockheed Aircraft Corporation (manufacturer's symbol)

 O -- Officer of Operations (USCG)

 O -- Organized Naval Reserve

 O1 -- Organized Naval Reserve Seagoing

 O2 -- Organized Naval Reserve Aviation

 OAA -- Radar Test Equipment

 OAD -- Officers' Accounts Division

 O&A Date -- Oath and Acceptance Date

 OAM -- Orthopedic Appliance Mechanic

 OAN -- Aids to Navigation Division (USCG)

 OANDOS -- Ordnance and Ordnance Stores (USCG)

 OAP -- Observation amphibian plane (USCG)

 OAS -- Occupied Areas Section (Military Government)

 OATC -- Oceanic Air Traffic Center

 OATC -- Overseas Air Traffic Control

 OAV -- Aviation Division (USCG)

 OB -- Operating Base

 OB -- Operational Base

 OB -- Ordnance Battalion

 OB -- Ordnance Board

 OBB -- Old Battleship

 OBJ -- Radar training device

 Oboe -- "O" in the phonetic alphabet

 OBR -- Office of Budget and Reports

*OBS -- Observatory

 ObsRon -- Observation Squadron

 OBSY -- Observatory

 OC -- Communications Division (USCG)

 OC -- Office of Censorship

 OC -- Officer Candidate (Army)

 OC -- Officer Commanding (USMC)

 O/C -- Officer-in-Charge (Army)

 OCAS -- Officer-in-Charge of Armament Supply

 Occ -- Occulting

 OCD -- Officer of Civilian Defense

 OCE -- Officer Conducting the Exercise

 OCJ -- Radar Training Device

 OCL -- Old Light Cruiser

 OCL -- Ordnance Circular Letters

 OCNPR -- Operation and Conservation of Naval Petroleum Reserves (appropriation title)

 OCR -- Office of Civilian Requirements (WPB)

 OCS -- Office of Contract Settlement

 OCS -- Officer Candidate School (Army)

 OCSigO -- Office of the Chief Signal Officer (Army)

 OCT -- Office of the Chief of Transportation (Army)

 OCV -- Old Aircraft Carrier

 OD -- Officer-of-the-Day

 OD -- Ordnance Data (inspection and test data)

 ODD -- Old Destroyer

 ODP -- Organized Reservists in drill pay status

 ODT -- Office of Defense Transportation

 OEG -- Operations Evaluation Group

 OEM -- Officer of Emergency management

 OEW -- Office of Economic Warfare

*OF -- Office(r)

 OFEA -- Office of Foreign Economic (Lend-Lease) Administration

 OFEC -- Office of Foreign Economic Coordination

 OFERRA -- Office of Foreign Economic Relief and Rehabilitation Administration

 Off -- Office(r)

 OffNavHist -- Office of Naval History

 OFLC -- Office of Foreign liquidation Commission

 OFP -- Operating Force Plan

 OFRR -- Office of Foreign Relief and Rehabilitation

 OFRRO -- Office of Foreign Relief and Rehabilitation Operations

 OFS -- Office of Field Service (OSRD)

 OFT -- Operational Flight Trainer

 OFU -- Floating Units Division (USCG)

 OG -- Officer of the Guard (Army)

 OGC -- Office of General Counsel

 OGR -- Ordnance, Gunnery and Readiness Division (USCG)

 OGU -- Outgoing Unit

 OHI -- Ordnance Handling Instructions

 OIAA -- Office of Inter-American Affairs

 OIC -- Officer-in-Charge

 OIL -- Ordnance Investigation Laboratory

 OinC or OINC -- Officer-in-Charge

 OinCABCCTC -- Officer-in-Charge, Advanced Base Combat Communication Training Center (Pearl Harbor)

 OIR -- Office of Industrial Relations (previously SECP)

"Oka" -- Japanese rocket-propelled one man guided missile; also called "Cherry Blossom"

 OKLA -- Oklahoma

 OLLA -- Office of Lend-Lease Administration

 OLP -- Observation landplane (USCG)

 OLP -- Office of Labor Production (WPB)

 O&LS -- Ocean and Lake Surveys (Navy) (appropriation title)

 OM -- Officer Messenger

 OM -- Order of Merit

 OME -- Office of Management Engineer

 OMGUS -- Office of Military Government United States

 OMI -- Ordnance Modifications Instructions

 OMM -- Officer Messenger Mail

 OMMC -- Officer Messenger Mail Center

 OMM(S)C -- Officer Messenger Mail (Sub) Center

 OMPUS -- Official Munitions Production United States

 ON -- Liverpool to New York, fast (routing designation)

#ONBOSUB -- And on board a submarine of that (fleet, force, squadron, or division, as appropriate)

#ONBOWOOM -- For duty on board that vessel when placed in commission

#ONBOWSERV -- For duty on board that vessel when placed in service

 ONH -- Office of Naval History

 ONI -- Office of Naval Intelligence

 ONM -- Liverpool to New York, medium (routing designation)

 ONOP -- Office of Naval Officer Procurement

*ONOP -- Officer-in-Charge, Branch Office of Naval Officer Procurement

 ONR -- Office of naval Research (formerly Office of Research and Inventions) (ORI))

 ONS -- Liverpool to Halifax, slow (routing designation)

 OOD -- Officer-of-the-Deck

 O&OS -- Ordnance and Ordnance Stores, Navy (appropriation title)

 OP -- Observation post (USMC)

 OP -- Office of Chief of Naval Operations

 Op 1 (2, etc.) -- Division 1 (2, etc.) of Office of CNO

*OP -- Operating; Operator; Operation(al)

 OP -- Operational Priority

 OP -- Ordnance Pamphlets

 OP -- Ordnance Personnel

 OPA -- Office of Price Administration

 OpAttyGen -- Opinion of the Attorney General

 OPC -- Optician

 Op-Com -- Operations-Communications

 OPD -- Operations Division (War Department, General Staff)

 OpDevFor -- Operations Development Forces

 Oper -- Operator

 Opers -- Operations

 OPET -- Organization, Personnel Equipment and Training (Group)

 OP&I -- Office of Patents and Inventions

 OpIntel -- Operational Intelligence

 OPL -- Outpost Line (Army)

 OPLR -- Outpost Line of Resistance (Army)

 OP&M -- Office of Procurement and Material

 OPM -- Office of Production Management

 OPM -- Optometrist

 OPMG -- Office of Provost Marshal General (also PMGO)

 OpNav -- Office of the Chief of Naval Operations; short title: CNO

 OP Plan -- Operating Plan

 OPR -- Office of Public Relations

 Opr -- Operator

 OPS -- Operations

 Op(s)ArmyJAG -- Opinion(s) of the Army Judge Advocate General

 OPT -- Optician

 OpTra -- Air Operational Training

 OPU -- Overseas Plexiglass Unit

 OQMG -- Office of the Quartermaster General (Army)

 OR -- Operations Room

 OR -- Orange, Texas

 ORA -- Organization de Resistance de L'Armée (France)

 Orange -- War plans for use in war against Japan

 ORC -- Officers' Reserve Corps (Army)

 ORD -- Office of Rubber Director (WPB)

 Ord -- Orderly

*ORD -- Ordnance

 ORDALT -- Ordnance Alterations

 ORDC -- Ordnance Research and Development Center (Aberdeen Proving Grounds, Maryland)

#ORDCAN -- Orders (identified by date or dispatch reference numbers following) are hereby cancelled

#ORDCOR -- Orders (identified by date or dispatch reference numbers following) are hereby corrected

 ORD DIS -- Ordinary Discharge

 Ord Eng -- Ordnance Engineering

#ORDMOD -- Orders (identified by date or dispatch reference numbers following) are hereby modified

 ORE -- Oregon

 ORG -- Operations Research Group

 ORI -- Office of Research and Inventions; now, Office of Naval Research ONR

 Orig -- Original

 ORIG -- Originator

 ORT -- Operating Room Technician

 OS -- First two letters in the Navy aircraft designation, indicating an observation-scouting plane

 OS -- Ordnance Specifications

 Osc -- Oscillator

 OSC -- Own ship's course

 OS&D or OS/D -- Over, Short, and Damaged (Report) (Army)

 OSFCW -- Office of Solid Fuels Coordinator

 OSigO -- Office of Chief Signal Officer

 OS2N -- "Kingfisher"; single-engine Navy scout-observation (VSO), seaplane, manufactured by Naval Aircraft Factory

 OSRD -- Office of Scientific Research and Development

 OSS -- Office of Strategic Services; now, SSU

 OSS -- Old Submarine

 OSTD -- Ordnance Standards

 OSU -- Shore Units Division (USCG)

 OS2U -- "Kingfisher"; single-engine Navy scout-observation (VSO), landplane and seaplane, manufactured by Vought-Sikorsky

 OSW -- Office of Secretary of War

 OT -- Aruba or Curaçoa to Northwest Africa (routing designation)

 OT -- Curaçoa to Trinidad (routing designation)

 OT -- New York to Netherlands West Indies (routing designation)

 OT -- Occupational Therapy Technician

 OTC -- Officer-in-Tactical Command

 OTC -- Officers' Training School

 OTCLant -- Fleet Operational Training Command, Atlantic (usually COTCLant)

 OTCPac -- Fleet Operational Training Command, Pacific (usually COTCPac)

 OTI -- Ordnance Technical Instructions

 OTU -- Operational Training Unit

 OUSW -- Office of the Under Secretary of War

 OVPD -- Overpaid

 O-V(RS) -- USNR designation for ordnance officers, commissioned and warrant, including radio electricians, qualified for specialist duties. This classification was abolished in September 1944 and replaced by the proper aviation or engineering classification with the suffix "T".

 O-V(S) -- USNR designation for ordnance officers, commissioned and warrant, including gunners and torpedomen, qualified for specialist duties. This classification was abolished in September 1944 and replaced by one of the following: (D), (D)L, (S), S(O), or S(O) with proper numeral indicating particular specialty within ordnance.

 OWI -- Office of War Information

 OWM -- Office of War Mobilization

 OWM&R -- Office of War Mobilization and Reconversion

 OWU -- Office of War Utilities (WPB)

 OY-# -- "Sentinel"; observation-scout (VOS), manufactured by Consolidated-Vultee

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Navy Numbers