The 57′ bow-ended design followed on from the 70′ coaches introduced in 1922 and were externally similar. When first introduced they went into premier express services, often in 6 coach sets, on trains such as The Bristolian and the Cheltenham Flyer. They were dispersed more widely as newer designs were introduced.
Left hand coaches had the first class compartments on the left viewed from the corridor side. Comet Models W57S is the right hand version.