The line that is the inspiration for my latest endeavours, the RTM, had a steel bodied 15 metre dining car which survives at Ouddorp and is being restored. I seem to think it was built in the early 1930s and was, technically speaking, a rebuild of an earlier vehicle. At the moment Ouddorp is building a replica of the last of the RTM Box Locos No.37, which survived into the late 50s, but not into preservation after 1966.
From the odds and ends I have gleaned about RTM engineering and accountancy practices the Dining Car may have been almost a new vehicle, but because of restrictions on the capital account it may have been put through the books as a rebuild. This tendancy got stronger in the 1950s after NS took a large stake in the RTM. They were only interested in the Tramway's bus services, so any expenditure on new equipment for the rail side of operations had to be hidden in plain sight, as NS had little interest in seeing the narrow gauge operations continue.
If my line ever runs to a catering vehicle it is most likely to be wooden bodied 13 metre carriage adapted into a 'bar car' for dishing out the cold Heineken and snacks to homeward bound commuters. :D
My other favourite railway - the IMR has a bar set adapted from three of the 1905 saloons in the early 1980s. Of the 1905 build of carriages the six saloons survive, but the two brake-luggage-thirds "half vans' have been broken up

Indeed of the half-vans only F43 and F49 survive, most of the others have gone since Nationalisation in 1978.
Peter in AZ