Looks a similar vintage to the 1934 Ruston diesels I've started. No glowplugs on them and compressed air starting.
The ones I ran were running a DC generator for a radio transmitter that was still in service in the early 1980's having been installed in 1934. I believe a museum now has one of the engines.
Exposed valve-gear, side rockers, oilers to be filled, a big JAP dog ear really!
