Is the glass/plexi tinted on a MC upright ? It is on the cabaret, and such small imperfections are invisible because of that. (Also, the cabaret really has a "hood" that protects the screen from any light from the surroundings.)
I usually want to stick to original too, but sometimes....... f.i. I totally hate the brown/bronze colored plexi's that Atari used a lot.
I replaced the original (that was full of cigarette burns) with a "grey" or colorless tinted plexi. This means that the colors of the CRT are the true colors, not the brown tinted one's.
Anyway, getting carried away here. I wish I had a full-size MC
I've used the marker pen method too, also only when it's not too visible (maybe that's how I did the SW bezel.....if only I'd remember
).