 Following trials with two Swiss-built trolleybuses, Coimbra in Portugal ordered six Sunbeams in 1950, with a view to replacing the tram system if they proved successful.The vehicles supplied were based on Sunbeam's MF2B model, with two axles and a wheelbase of .They were fitted with single deck bodywork by Park Royal Vehicles, with 40 seats and room for 35 standing passengers.