Gladys, may i put a few thoughts into this subject. From (past) history, my very good friend Gino Biffany gave the marble world this term, because he had worked with wiring he considered (tracer) type wiring in his younger days. This is a (generalized) term handed down because of the (white) opaque thinner line that accompanied another color. This being said, i do (think) that not ONLY Peltier had this (tracer) type configuration also maybe in other makers. I like to think of it as more in Peltier more than others though, in (honor) of Gino. YES, i have found more in Peltier that there are other family types that could or may lie in this category. The base glass in these are in the translucent color more than others, you will find. I have found that finding a (tracer) type in clear is another subject to tackle or even an opaque base color. Keeping this like Gino had mentioned makes it much easier for the NEW collector. Chuck G---