What is this undercoating material, Not your normal rubber stuff Options

[Mikey914]

So cleaning up the bottom of the car to assess the entire car, and found this material that looks like a light coat of primer. It has enough grime on it to be original.
My question to anyone that was around when these were coming out of the dealerships is; what is it, and what was it supposed to do? There is no rust so it certainly worked, but this was a Nevada car all its life.

Mr Mayer perhaps you have an idea?

[Mikey914]

Thanks Andy,
Definitely has a different texture. It doesn't seen to be a faded paint underneath, as its pretty uniform. My inpression is that it may have the PVC base coat, but also has a coating over the paint. I did try removing it in a small section and was able to het more color to show with a solvent. Mt search now is for the original material it was coared with on tbe outside.