sorry this is a very late response...
my display (before I sold it with a system) used to be the same.

but yes. they're is a coating. methylated spirits, warm water, a soft cloth stripped it off. only a little bit of pressure needed

Click to expand...

Hey Tom you are a genius!

I started off using Isopropyl Alcohol on cotton wool but found that an awful lot of pressure was required and the coating was lifting off painfully slowly. I tried warm soapy water but this did not touch it at all.

I then remembered that some time ago my wife bought some 'magic' cloths from the local supermarket. The're called 'No More Chemicals' and are a cotton cloth impregnated with silver. They are very smooth but somehow the silver helps the cleaning.

This cloth dampened with IPA cleaned the whole screen in under 5 minutes - it looks as good as new

Thanks for helping out!