What is "silverliner"

Silverliner is the name given to a series of electric multiple unit railcars in commuter rail service in the Philadelphia area since 1958. As of the introduction of the Silverliner V in 2009-2010, there have been 5 generations of Silverliner cars, identified by the Roman numerals I through V placed after the name Silverliner. The Silverliner name came from the classes' shiny stainless steel body shell compared with the painted (or rusting) carbon steel railcars placed in service by the Pennsylvania and Reading Railroads between 1915 and 1936. Applied to the first large production order in 1963, the cars made such an impression that the name has since been applied to all subsequent MU classes purchased by SEPTA for the Regional Rail services.