Between 1967 and 1971, seventy five general purpose flat wagons were placed into service. The class was SKX and the numbers were 1 to 75.
Between 1972 and 1974, seven SKX wagons were fitted with special container fittings and classed SKF_. The SKX wagons recoded were 13, 14, 44 - 47, 71.
In the 1979 recoding the class was relettered to VFKX.
The class was relettered between 1979 and 1982.
VFKX numbers were: 1 - 12, 15 - 43, 48 - 70, 72 - 75.
In 1984, fifteen VFKX wagons were modified with side cranes and bolsters for welded rail transports. They were reclassed to VFRX.
Between 1990 and 1991 the remaining wagons were reclassed to VEKX, VKKX or VQKX.