Is This a Paint Color or Undercoat??

[Schmierung]

Cleaning up a 1974, Schwartz/Black and found strange color in engine compartment. Can someone identify this? I have always seen body color in engine compartment unless repaint. The color here does not look like any body color. I included a black paint cap for comparison.
Intention was to spray black but if this is something unique??
Thoughts are appreciated.

[nathanbs]

It looks like gray body shutz that didn’t get painted black.

[Schmierung]

Thanks Nathan.
Would it be more interesting to let it alone rather than painting it black to match?
Interesting...

[nathanbs]

It’s interesting to me as an original sort of defect or flaw. It’s popular/common to reproduce or embrace these factory quirks