sentences:  He introduced the first composite welded steel/timber bodies with standardised jig-built components.The first open carriages, referred to as "vestibule coaches", also appeared.From 1933, roofs were of steel rather than wood, with a simplified livery and a smoother external appearance, and, at the end of the 1930s all-welded steel vehicles were built for the Liverpool and Southport electric service, the Class 502.