- Oldsmobile Division, General Motors Corporation, 1942 (1)
- Oliver & Boyd (Edinburgh) (1)
- Oliver Ditson & Co (Boston) (2)
- Oliver Ditson & Co. (Boston) (1)
- Oliver Ditson (Boston) (3)
- Oliver Ditson Company (Boston), 1920 (1)
- Oliver Ditson Company (Boston, Massachucetts), 1919 (1)
- Oliver Iron Mining Co., Mining Engineering Dept. ; Duluth, Minnesota (1)
- Ommation Press (Chicago) (1)
- On sale at U.S. Lake Survey Office (Detroit, Mich) (1)
- On sale at U.S. Lake Survey Office (Detroit, Michigan) (1)
- Opus Playhouse (1)
- Orchid Album: Comprising Coloured Figures and Descriptions of New, Rare and Orchidaceous Plants. London: B.S. Williams (London) (2)
- Ordered by the House of Commons to be printed ; London (1)
- Ordnance Survey (Dublin) (1)
- Ordnance Survey (England) (1)
- Ordnance Survey (London) (2)
- Ordnance Survey Office (Richmond upon Thames, London?) (1)
- Ordnance Survey Office (Southampton) (5)
- Oregon State Highway Commission (Salem, Or) (2)
