Though, with these two examples which do not have an actual lunette of different color than the plaque, they were made with translucent plastics almost as if the entire plaque was a lunette. The contour of the surface in my photo is also the same as the two CG images; it was part of the molding process with these and, just an assumption here; the pigments added to the mixture is probably what made the finished plaques durable (hard-wearing) than what would normally be the case with clearer lunettes back then... which early on were unprotected.

Though I am not a scientist, I strongly believe temperature and humidity play an important part in what we see with most of the earlier plastic laminates, since there rests in some very well-maintained collections early Monaco pieces contained which are in their original state of preservation as if they were just made yesterday, compared to some of we have all tossed due to be badly damaged.