Part way through 1977, a small percentage of bogie exchange wagons were recoded from "X" to "F" which reduced their interchange ability. This would not prevent a vehicle being bogie exchanged but would restrict the class to whatever gauge they were on. Some classes retained the grade control equipment. All classes were returned to broad gauge.
The reason for this change was that all states were required to provide a percentage of bogies and parts to other states based on the percentage of owning state wagon numbers in the "pool". To reduce the cost of providing bogies and equipment, VR/Vicrail reduced the bogie exchange numbers by reclassing "X" wagons to "F".
Classes affected were FQX_ ( 100 number ), JCX_, JDX, JQX_ and JSX_.
File m1977m compiled by Peter J. Vincent, 14/2/2007