Multi-component synthetic closure and method of manufacture thereof

A multi-component synthetic closure and/or a rod-shaped intermediate product which incorporate printed indicia comprising ink that is invisible under normal lighting and/or temperature conditions and a continuous, in-line manufacturing process therefor are described. In the preferred embodiment of the present disclosure, the core member of the synthetic closure and/or the rod-shaped intermediate product can be formed by a continuous extrusion process which enables the core to be manufactured as an elongated, continuous length of material. As the continuous elongated length of extruded material forming the central core is advanced from the extruder towards an outer skin forming station, the central core passes through a printing station for forming any desired indicia among which can be a registration mark that can be invisible under normal lighting and/or temperature conditions on the outer surface of the central core prior to the application of the outer skin layer.