Hey Migs,
That reflector appears to be stock/un-modified, and has simply had it's coating degrade over time.
In the side profile pic of the reflector, you can see the defined, yet asymmetrical edge of the coating where it overlaps onto the outside surface. It looks the same as all other Mag C/D reflectors (and many others). A spray paint job would produce a very different look to that edge.
Additionally, paint would tend to stay on the reflector as opposed to evaporating (if that's actually the correct physical process happening), which the coating on this reflector is doing, and is the reason for the blue showing through, as well as the gritty feel. I've seen this on more than one, but for example, the reflector from my very first flashlight (I was about 10 at the time) suffered the same fate to an even larger degree. I kept it after modding the light about a year and a half ago, and will snap some pics of it soon. The degradation looks similar to yours, except add another 20 years sitting in the garage with no lens. The coating is almost gone!
Since the vacuum deposition method involves evaporated particles to create the coating, I wonder if they can evaporate off over time if not well protected? :shrug: That might explain why the coating seems to just "disappear", revealing the plastic underneath. I also wonder how much of a role oxidation might play since the particles are usually aluminum (or "aluminized", whatever that means).
Hope that helps!
