train at Pukerua Bay station north of Wellington, 1930

It could be an original Wellington and Manawatu Railway Company passenger car which were clerestory roofed. The station building is the original WMR's 20 x 10 foot “shelter shed” built in 1886. This was a flag station, meaning it was not a timetabled stop -- passengers wanting to get off there had to let the train guard know by the previous timetabled station(s). 

The line was electrified through here circa 1940 and upon opening of the Wellington to Paekakariki electrification, steam-hauled trains became rare.