O scale (or O gauge) is a commonly used railway modeling scale introduced by German toy manufacturer Marklin around 1900. Until the early 1960s, the O scale was the most popular model railroad scale in the United States. The popularity of the scale declined in Europe before the Second World War due to smaller scales.
O scale was in its prime when model railroads were seen as toys. With more attention on cost, durability, and the ability to be easily handled and operated by pre-adult hands. There was not much emphasis on details and realism. O scale is still a popular choice for model railroaders who enjoy running trains more than other aspects of modeling. However, recent developments have addressed scale model railroaders making the O scale popular among fine-scale modelers. For those who value the detail that can be achieved. The size of O is larger than OO/HO layouts and thus is a factor in deciding to build an O scale layout. Collecting vintage O scale trains is also popular, and there is a market for both reproduction and vintage models.
The name for O gauge and O scale is derived from “0 [zero] gauge” or “Gauge O,” being smaller than Gauge 1 and the other then-existing standards. It was created in part because manufacturers realized their best-selling trains were those built in the smaller scales.
Manufacturers such as the Ives Manufacturing Company, American Flyer, and Lionel Corporation used O gauge for their budget line in the United States. Marketing either Gauge 1 or ‘Wide gauge’ (also known as ‘standard gauge’) as their premium trains. One of the Lionel Corporation’s most popular trains, the 203 Armoured Locomotive. O gauge and ran on tracks with rails spaced 1.25 inches apart. The Great Depression wiped out demand for the expensive larger trains, and by 1932, O gauge was the standard, almost by default.
Since the early 1990s, O scale manufacturers have begun placing more emphasis on realism. The scale has experienced a resurgence in popularity. However, it remains less popular than HO or N scale. However, newer manufacturers, including MTH Electric Trains, Lionel, LLC, Atlas Model Railroad Co, and Weavermodels. Make very exact, 1:48 scale models of trains.
O Scale in the UK is commonly 1:43.5 or 7 mm to the foot. In continental Europe, it is commonly 1:45 though 1:43.5 is also used particularly in France, and in the USA 1:48. Each region tends to design models to its own scale. The NMRA and the MOROP maintain detailed standards for various scales to help model makers create interoperable models.