Sitting here looking at my SM300 crystal and its awful, every time I wear this thick weave linen shirt (and I love linen, half my shirts are linen) I end up putting a matte finish on the peak of the domed crystal. For some reason the tophat plexi on the 1680 Submariner is impervious to scratches, must be something about the design that takes scratches to the edge rather than the surface and hides it better, but do you guys ever have issues with shirts scuffing up plexi crystals?
Everything seems to scuff up Hesalite. Good thing it polishes easily. I bet you could get a sapphire replacement and store away the other. It's not like it's an original anyway, right?
Linen is far rougher than cotton. I don't think sapphire will work for the 300, unless it's a newer one. Sounds like Polywatch and Q-tips for you, gatorcpa