hp-15C faceplate

[Flare]

Please see the attached image of my 1985 15C.
I did some research but I reckoned you guys would know best.

What has happened to the faceplate where it is white/grey?

I have read there is a clearcoat, has this been scratched away allowing the aluminium to oxidise? The white parts seem to be raised but I can't get it off with IPA.

I was thinking of following the guide in post 10 of this thread:
https://www.hpmuseum.org/cgi-sys/cgiwrap...ead=153539
But I would like to know exactly what the issue is before sanding it.

Is there a known way to deal with this, also did that book on calculator restoration ever materialise?

Thanks.