Although these coaches were in production for a relatively short period they came to be as much recognised as the earlier Gresley designs. They had steel flush sides, straight roof and the graceful oval toilet windows were distinctive. Initially all Thompson designs followed Gresley practice in having square cornered windows, which led to continual problems of rusting in the bottom corners. In an attempt to combat this the later builds had rounded corners to the windows, as depicted by the etch.
The restaurant first ran with either an open third (Comet Models E17) or restaurant pantry third (E15).