One of 27 such trailers built by Boon and Co of Christchurch between 1917 and 1923. They were built to replace the old double deck trailers taken over from the private tramway companies by the ChristchurchTramway Board in 1905.

Earlier cars had a 4 wheel Peckham P22 radial axle track, but 201 to 206 had Brill 4 wheel Radiax trucks. (The Society has a Radiax truck - this is currently used under the Society's ballast wagon).

Three of these trailers - 203 - 205 were converted to one-man trams, initially as an  experiment in 1920's where they were referred to as "St Martins" cars by the public as they were primarily used on this route. They were withdrawn as trams in 1939. 205 was later converted back into a trailer, and 203 was later used as a bicycle tram. However 202 remained as a trailer throughout its working life.