A total of 135 examples of this Co-Co type were manufactured between 1976 and 1984, 30 in Romania and 105 in Britain (the Romanian ones subsequently required extensive overhauls). They were designed for heavy freight work. "It is a Type 5 locomotive, with a Ruston-Paxman power unit developing 3,250 bhp (2,423 kW)... Enthusiasts nicknamed them "Gridirons" (or "Grids" for short), due to the grid-like horn cover on the locomotive's cab ends fitted to nos. 56056 onwards. Under its Romanian railway factory nomenclature, the locomotive was named Electroputere LDE 3500, with LDE coming from Locomotivă Diesel-Electrică (Diesel-Electric Locomotive) and the 3500 being the planned horsepower output."