GTA spare rear lights, opaque cover?

I'm in the process of recommissioning my GTA turbo that's been tucked away for a few years. It prompted me to have a rummage through my parts boxes and I'd totally forgotten she came with a set of rear lights.



As you can see, left hand light is in pretty good nick but the right hand one has a strange tint to its cover. Is this some form of ageing process whereby the cover becomes opaque or is it someone's really sh*t effort at a smoked tint??

The light itself appear in good condition under the opaque cover.

They were never made like that so either someone has sprayed it to apply a tint or they have applied some sort of film. I am not aware of aging causing this problem.
If it is not a film then I would suggest you try one of these plastic headlamp resoration kits (start, if you can, in a hidden part) and see what the effect is

I cleaned up my A310 rear lights (and those on the Dyane) soaking the lenses in some coffee machine cleaner. They came up looking like new.

Thanks for the advice guys... still working on some mechanicals but will address this in good time