The S-Class W140 is a series of flagship vehicles that were manufactured Mercedes-Benz. The W140 premiered at the Geneva Motor Show in March 1991. Short (SE) and long (SEL) wheelbase sedans were offered initially, as well as the coupé (SEC) body style from October 1992. Like all Mercedes-Benz lines, the W140 S-Class was rationalized in late 1993 using the new "letter-first" nomenclature. The SE, SEL, and SEC cars were renamed the S-Class, with alphanumerical designations inverted. For example, the 500 SE became the S 500, and the 500 SEL became the S 500 L.
As with its predecessor, the W140 was the first of the "next generation" of Mercedes-Benz models to feature the company's new design theme. The W140 S-Class introduced several safety innovations which have since become commonplace among many vehicles.
Source: Wikipedia, 2012