A guy down the road from me thinks he might be able to rotary polish old plastics back to their former glory. So were looking for a rough test panel for free of course. But you might get it back all shiney.
I have a blue IT mudguard, 1977 and in need of a buff!!
But there's no mystery to it, sand paper to get it back to colour and smooth out scatches, then finer and finer and finish with a polish or a hot air gun to bring back the shine. Hard work though! hence most of mine are half done!