George Gourko also made the mirror cells. Three sets of push screws and spring-loaded pull screws adjust the mirror. The plates are wood with ventilation holes. The mirror is held to the upper plate with 6 large drops of silicone rubber cement (aquarium glue), three on the bottom and three through holes (not visible in the image because they're filled with glue) in steel angle brackets that act as a back-up support in case the bottom silicone comes loose. The mirror was supported on coins on the upper plates until the glue dried, so it rests on the glue rather than the wood.
Bottom view showing the ventilation holes.