[lip277]

Yeah - the yellowing is not going away (and was there when I got the sign).

It appears to be acrylic. The surface is not 'dirty' as such - it's just not smooth (with added defects/pitting/scratches) in places to add to the look. lol

That patina is what I am wanting to minimize - as best I can.
Did some searching before - and will do more (not finding much so far, so why I asked here).

The mat finish is my main focus - just so it looks like a sign should when illuminated from behind.

Will see how this goes...