This engine was called the "Mule of the Giovi Pass” an alternating current-powered locomotive created to handle winding Italian mountain passes. Lightweight and powerful, it replaced the 470, which was twice as large but half as powerful, easing the difficult journey through the Ligurian Apennines. These characteristics made the engine useful during World War I as a way to transport men and equipment through the major Alpine passes. The E550 was also revolutionary from another point of view: saving workers the backbreaking and dangerous work of the feeding the firebox in tunnels. With the advent of the electric locomotive, drivers were no longer called “i musi neri,” or black faces. A dedicated factory for the production of the E550 was built in Vado Ligure and still exists today. These locomotives remained in service for more than 70 years.