Sector dials have been showing up on watches so often in modern collections that one could be forgiven for thinking that it's a new innovation--but the truth is that they're anything but. 

In fact, their recent popularity only proves the truth of the old adage "everything old is new again." 

The name "sector dial" comes from the markings on the dial that divide it into sectors. In most cases, the dial would contain the hours and minutes inside concentric circles, with the hours further separated by markers. Though the style is often referred to as a "railroad" style, due to its similarity to those used on railroad pocket watches, these two terms are not mutually exclusive and should not be confused.

Despite that similarity, the history of these dials is murky, and its origins can't be traced to any particular purpose, the railroad or otherwise. However, many trench watches used by officers in the First World War had sector dials. They began appearing on wristwatches in the late 1920s or 1930s, enjoying a period of popularity until they faded from catalogs in the 1950s. 

Brands from Omega to Patek Philippe used these dials, with the latter versions being particularly desirable. 

This is a gorgeous variant in stainless steel from Jaeger-LeCoultre. The use of the sector dial--as well as the numerals at 3, 6, 9, and 12--are a subtle foreshadowing of the current JLC Master Control series. But while the dials of the current Master Control collection are two-tone, this is a stunning salmon overall.

Examples like this watch illustrate the undying appeal of this classic mid-century design.