O

O: Official. Scott catalog number prefix to identify stamps other than standard postage.
O B H V: Osterreichischer Briefmarken-Verband, Austrian Stamp Dealers Association
OBLITERATION: Term used to denote a cancellation marking.
OBSOLETE: Stamps that are no longer sold by the postal service.
O/C: Off centered design
OCCUPATION STAMPS: Stamps issued for use in enemy territories by the conquerors.
ODDITIES: Stamps that have design errors, gum varieties, shade differences, etc.
ODONTOMETRE: 1866 name for perforation gauge.
OFF CENTER: A stamp design that is not printed in the exact center of the paper.
OFFICES ABROAD: Postal agency of one country in another, usually because of the poor local postal network. Special stamps were usually overprinted for these offices, mainly from the country maintaining the office.
OFFICIAL REPRINT: Stamps reprinted at a later date by the original issuing entity from the original plates.
OFFICIAL SEAL: A label, in stamp form, issued by the Post Office to seal mail and parcel post that has opened in transit or that may have been opened for postal inspection of contents.
OFFICIAL STAMPS: A government agency postage stamp.
OFF PAPER: Stamps that have been soaked off the paper.
OFFSET: Reverse impression from the face of a sheet of stamps onto the back of another sheet.
OFFSET LITHOGRAPHY: This printing process consists of transferring an image from an aluminum or zinc plate to a rubber blanket. The image is then transferred from the rubber blanket to the paper running through the machine.
OG: Term for Original Gum as applied when the stamp was printed.
O H M S: On His/Her Majesty's Service.
OL: Local official. Scott catalog number prefix to identify stamps other than standard postage.
OLS: Outer Letter Sheet
OMNIBUS ISSUE: A common theme used on the stamps of several different countries.
OnB: On Board (Zeppelin Mail cachet)
ON COVER: Stamps that are on the original envelope and may also be "tied" (postmark on stamp and cover tying the two together) to cover.
ON PAPER: Stamps that still have paper portions of the original envelope or wrapper stuck to them.
ON PIECE: A stamp attached to the original portion of the envelope or wrapper with enough of the cancel showing to ensure authenticity.
O P A T: Organiacion Panamenta Antituberculosa, the Panama Tuberculosis Organization.
OPP: Opposite
OPT or OVPT: Overprint
OPTICAL CHARACTER READER (OCR): Mail-processing machine that "reads" an address and translates it into a sprayed on bar code.
OPTIFORMA PRESS: Six-color Goebel press used by the BEP.
ORANGEBURG COIL: Issued January 24, 1911, in Orangeburg, NY, for the Bell Pharmaceutical Co.
ORD: Ordinary (paper)
ORDINARY USAGE: The correct rate of postage applied for the correct usage.
ORIGINAL: A stamp from the first issue and not a reprint or later issue.
ORIGINAL GUM: Gum which is in the original state as applied by the printer and appears untouched by a hinge.
OSS FORGERIES: Office of Strategic Services postal forgeries for use in Japanese-occupied China during World War II
OVER (or UNDER) INKING: Stamps that have been received with more or less of one or more of the colors to complete the design.
OVERCHARGE: See surcharge
OVERLAY: Overall printing, usually applied to light weight papers to make them opaque so that any writing on the inside is not visible outside.
OVERPRINT: An additional printing on a stamp that was not part of the original design. For example, the Molly Pitcher U.S. stamp of 1928.
OVPT(D): Overprint(ed)
OWLS: Mail carriers in the magical world of Harry Potter.
OX: U.S. Post Office Official Seals. Scott catalog number prefix to identify stamps other than standard postage.
OXIDIZED: Term applied to a stamp that has been darkened from sulphurization or oxidation with age.
OY: New Zealand Life Insurance. Scott catalog number prefix to identify stamps other than standard postage.