The KMC wagons were introduced for "Mayne Nicklaus" traffic, hence the 'M' in the code. "Mayne Nicklaus" was a road transport company operating Victorian and interstate services.
The KMC's could carry two LCL containers.
There were three wagons numbered 1, 2 and 3. They were converted from _KC_ wagons in 1963.
By the mid 1970's, this traffic was gone. The wagons were in service with _KC_ flat wagons hauling tallow containers.
They were out of service by the mid 1980's.
In 1981 two KMQ_ were incorrectly lettered "KMC".