The O class were in service from the 1860's and were used to transport coal from the ships at Port Melbourne/Williamstown/Geelong to Melbourne. Presumed coal use was for steam enngines.
A coal strike in NSW in the 1900's accelerated local coal production to serve the railways. The 'State Mine' at Wonthaggi opened in 1910 and the transhipment of coal stopped apart from 'Lithgow' coal for some passenger engines. The oldest O wagons were scrapped and the fleet reduced in size by 25%.
The 1908 electrification plan for Melbourne included construction of a power station. Suitable coal was obtainable at Yallourn, 140km east. For traffic, the railways built one hundred and eighty three 'O' wagons between 1915 and 1923. Of interest, the German equipment for the brown coal open cut was obtained as reparation payment from 'The Great War'.
From 1936 to 1960 the older 10t small hopper wagons were scrapped, as unsuitable in capacity or autocoupler conversion.
From the late 1950's, O wagons were required for different traffic. Some were converted to ballast traffic and became _ON_. These wagons were reclassed back to O wagons some 18 months later for coal traffic Geelong to Ballarat. Most of these wagons were later converted to _OC_.
In later 1960's, some wagons were used for dedicated limestone traffic in Gippsland.
The number group was 1 - 388
1 - 40: Built New 1870/71, 10ton capacity
1 - 5: (2nd) NN to O conversions 1920
41 - 60: Built 1881-1883. These were wooden trucks, not hopper vehicles
61 - 104: (1st) Taken over from HBUR Co. All scrapped by 1889
61 - 104: (2nd) Built 1889
105 - 154: Built 1886/87.
155 - 209: Built 1889 - 1890. O 23 rebuilt
210: Ex duplicate O 153
211 - 212: Built 1915, 16 ton capacity
213 - 260: Built 1916
261 - 310: Built 1919
311 - 335: Built 1920
334 - 388: Built 1923. Nos 334 - 338, 345 built for pulverised coal tests
O 1 - 5
These wagons were the start of a program to convert all the bogie _NN__ ballast wagons to O four wheel hoppers for power station coal traffic. The O numbers 1 to 5 were re-used
O 211 - 388
'Standard' 15ton hopper with 'pin' latched drop doors.