Not gold but gold capped. There is a difference
A bigger picture of the dial straight on would help. Right now I'm thinking the dial has been refinished (a while ago) so a really nice close-up shot may prove me wrong.
« Plaque » means « plated ». You’ll notice it’s almost the same word. Lunette is bezel.
So indeed the inscription says, literally «gold plated bezel, 80 microns »
This also makes me wonder about the mid-case. Also 80 microns plated? They could be reflections, but I think I might be seeing some base metal showing on the corners under the lugs.