According to Sodor "historian" Martin Clutterbuck, Gordon is supposed to be an experimental prototype for Sir Nigel Gresley's A1 "Pacific" design for the GNR - the so called "A0". Gordon was then built at Doncaster Works, Yorkshire, and tested against a similar NER Pacific in 1923. Gordon, being an experimental engine, never received a number, and was later rebuilt at Crewe with LMS underparts and a six-wheel tender, owning to various problems. Gordon has since been rebuilt below the footplate according to Stanier designs, his running plate being Sir Topham Hatt's own design.
Gordon is painted NWR blue with NWR red-and-yellow lining and the number "4" painted on his tender sides in yellow. Before arriving on Sodor, he was painted Doncaster green with white and black lining.