OK I'm still looking to find a picture of the pattern and a source for the correct grill cloth but that didn't stop me from putting it back together. It's running great, and the original clock is working after a good cleaning and a small repair. Very happy with this restore. Anyone with additional info other that what we have in the Gallery and the Library would be of great help.
They seemed to use one-off cloth for some models, while keeping the cloth uniform for others in the same model year. But I guess that is production line ways.
I can't help with the grille cloth pattern. My 570 had the cloth replaced by the previous owner. I've decided to install a variant of the 70/90 cloth that was made 20-odd years ago that I've had kicking around, as it looks nice.
When I'm in that situation I find a grille cloth that looks good but keep looking for something closer to original. Most times it's not too hard to switch to the new one.