I have an old C&S in white scales. These must have been made with a casein-based plastic rather than bakelite, as white bakelite is now amber/brown after all this time! I'm pretty sure the other C&S scales were bakelite rather than celluloid.

I think that the brown discolouration is evidence of chemical breakdown/oxidation. Sometimes it is just a mild surface bloom that can be eliminated by polishing. It is evidence that the glossy top layer is beginning to break-down and reveal the filler material.

Bakelite is a combination of phenol, formaldehyde and filler - usually wood-flour, asbestos or slate dust. Both phenol and formaldehyde have distinctive odours.

Polishing bakelite with simichrome is a test - no matter what colour the article is, a yellowish (sometimes tending towards pink) residue is left on the cloth. Another test is putting the object in hot water - a phenolic smell is released - hard to describe, but often reminds people of the smell of hospitals. Greater heats emit that carbolic acid smell, so distinctive of old over-heated electrical components.

Beeswax slows down the rate of breakdown, but will not eliminate it.

Regards,
Neil.