In 1974 a new 'modular' design hopper wagon was built. The wagons allowed for different top cover designs and bottom discharge features.
For sand traffic, used in the manufacture of glass products, twenty wagons were issued to traffic in 1974. The class was JSX and the numbers were 301 - 320.
To reduce the number of 'X' bogie exchange wagons in service, many wagon classes were relettered to 'F'. The JSX class became the JSF class. These changes took place from October 1977.
By late 1977, five more wagons were built, numbers 321 to 325. These wagons were delivered to Newport Workshops ex Ballarat as JSX. At Newport, they were repainted to JSF prior to release to traffic. They were photographed at Newport during October 1977 as JSF. This conflicts with official records which show the group 321 to 325 issued to service as JSX during December 1977.
JSX wagons 301 to 325 were recoded to JSF 301 to 325 by December 1977.
During 1978/1979 a further fifteen more wagons were built. These were numbers 326 to 340.
In the 1979 recoding the wagons were relettered to VHSY.