We are sometimes asked for traffolyte labels or plates

This is a brand name from early to mid 20th century used initially to identify specifications on transformers

They were made from layers of coloured phenolic resin when top layers were mechanically engraved, the colours beneath were revealed in the engraving.
Due to the later known hazards of phenolics there were replaced, and the brand no longer exists.

Today the plates are made from layers of Acrylic co-polymers which are not hazardous to use.

Mechanical engraving is not mostly replaced with laser engraving and cutting allowing for a more versatile range of engraved marking signs and products Check here for custom plates