This pair of 10" F2.0 gold-coated mirrors are fast primaries. They will be used as telescope mirrors in two spectrometers. The gold coatings (over-coated with SiO2) are applied to give the instrument sensitivity in the infra-red region of the spectrum.
The photo of the backs of the two mirrors shows the first coating layer that is applied. Evaporated golf won't stick to the borosilicate substrates, so the two mirrors were first coated with standard aluminum. So you don't see the gold coatings when you look at the back sides.
From the front, you can see the beautiful evaporated gold. After the gold layer is applied, the mirrors are finished with a standard SiO2 over-coating. These coatings were all applied by Jeff Decker at Majestic Coatings.