Although these coaches were in production for a relatively short period they came to be as much recognised as were the earlier Gresley designs. They had steel flush sides, straight roof, and narrow toplights. Like all full brakes they could be seen not only in their own region but throughout the system on passenger and parcels trains.
The first ten were built for the Flying Scotsman service and had the body panels extended down to the bottom of the solebar. This product represents the remaining 25 coaches, although at least one of the first ten had the extended panel removed.