The 4H4v12af Class is a class of semi-streamlined 4-8-4s designed by Conan Diedrich at the Eastern & Atlantic's Richmond Works.
The 4-8-4 wheel arrangement was found to be very good at high-speed, heavy passenger trains, and thus Conan Diedrich decided that, after the Second World War was over, a new express passenger locomotive with the 4-8-4 wheel arrangement was required. This locomotive took streamlining cues from the New Zealand Railways KA Class, which Conan Diedrich had seen on an international trip to get distinctive locomotive designs in 1946.
The Eastern & Atlantic had always had a thing for distinctive looking locomotives, and the 4H4v12af Class was no exception. The locomotives were put to work on such trains as the Wild Comet, from New York to Washington, DC, averaging speeds of over 100 mph on this heavy train. 15 locomotives were built at the Richmond works between 1947 and 1949.