To provide for open wagons on the new standard gauge ( S.G. ) link between Victoria and New South Wales, new wagons were built and some existing classes were modified for S.G. use.
Thirteen _E__ wagons were modified with roller bearing bogies and Grade Control equipment ( 'retainers' ). Ten were done in 1962 and three more in early 1965.
The wagons were grouped into the EF class with the E wagon numbers retained.
From late 1965 through to 1969, the wagons were modified as suitable for bogie exchange and reclassed _EX_ with new numbers.