'59 Cadillac Interior Metal Trim Cleaning

[BillR. CLC # 29203]

Good afternoon!!
Cleaning up trim pieces . 
Here's my question with regard to what I think are headliner interior trim pieces (2)  for the front and rear .
There's a sticky gray substance that's relatively easy to remove with finger nail, a stiff rag and spirits. However, there's some black material (looks like dried POR15) on the opposite side that might very well not show when installed but I have the urge to make it go away. My above method does not put a dent in it.
Any thoughts?
Thanks in advance.
Bill Rodwick 

[savemy67]

Hello Bill,

You could try something stronger than mineral spirits, like acetone.  Maybe try it in a small spot.  If acetone doesn't dissolve the coating, I would leave it be, if it does not show when installed.  That hard a coating may make for good protection.  Just a thought.

Christopher Winter

[BillR. CLC # 29203]

Christopher,
As usual thanks for your reply.
I believe I will do as you suggest once I'm sure the black substance streak won't show. I will clean and AustoSol polish the "business side" and do my best on the back side.
This trip I brought back 28 pieces of trim thinking that once I unwrapped them they'd be dinged or worse. Of the 28 only found one minor scratch that I am pretty sure I can tweak.
The owner and her husband, previous to my son, must have garaged it and parked smart.
Thanks. 
Bill Rodwick