Duke:
The bottom picture in your original post shows the "LAT-72 Motorola Radio Kit" for a Tiger. That description is straight out of the "bible of the Tiger hobby," known as "The Book of Norman." That particular picture, taken about six years ago, shows that radio kit in a Tiger Mk1A,
serial #B382001600LRXFE. How do I know this, you might ask? Because I'm the one who took the picture and it's my Tiger. I pieced that kit together off of Ebay and from parts ads over the years. When I got the speaker grille, it was the metallic color, not black. I, too, have only seen them in the metallic finish. Odds are that someone has painted that grille black in the first picture, although just as surely as I say that, there will be someone out there who will claim that they bought theirs new and it was black.
As far as cleaning the grille back to it's metallic finish, I was lucky in the fact that mine still had a good metallic finish to it. As I remember, the metal is pretty delicate and I'd hate to get after it too hard with anything. Maybe, just maybe, you could glass bead it at a very low pressure but I can't remember enough about it to be sure.
I've seen that radio mount and speaker grille with a variety of different radios installed, leading me to believe that the Motorola unit was not the only radio available with that kit. I do know, however, that the bright aluminum finish around the radio itself is different depending upon which radio you have.
If you need any more info or any further pictures of it, just let me know and I'd be glad to post some.
Take care,