Here is a really minor tip: If your shift knob 1-2-3-4 is really brown and nasty pop out the insert (notch at the top wrt reading the numbers) and soak it in bleach for a few hours. Whitens back up with no ill effects. Also, on M47 knobs, most have a heavy iron weight inside where the OD switch goes. Just noticed this fact. I guess it helps feel and throw.

OK, let me modify. Lets say a few hours in bleach. Overnight in bleach is too much and about half the black inserts start to lose pigment and go suller charcoal gray. I did about a dozen of them overnight and just noticed some effect on the insert. Enough on this subject.