Thanks, very interesting. There was a thread on TGP recently where a guy was asking about white that stays white. That's where I first learned the yellowing is in the clear coat. Like the article says, some of the originals where not clear-coated for some reason and that's why you get some vintage guitars in Olympic white that still looks like the arctic white of today.
If I recall correctly, Earl Slick asked for his signature Framus guitar not to be clear-coated, to give it more of a matte rock 'n roll look. Not a big fan of glass-like glossy finishes myself.