Abstract: In a system for individually marking electrical or mechanical components a conveyor belt apparatus for delivering the components to and from a marking device for marking thereby including first and second elongated, closed loop, endless belt elements spaced side by side in a parallel arrangement and adapted to be synchronously driven in a tractor-like manner and a carrier assembly for carrying the components to be marked including a longitudinal (in the direction of belt elongation) series of short length plate members for mounting to the first and second belt elements thereby forming a tractor belt with the belt elements and interchangeable upper members removably mounted to the plate member, each upper member holding a component thereon at least while the conveyor belt apparatus is delivering components.