These parts form the Faceplate and back Plate of the 737SS DU panel. The front panel is created from 3mm white acyrilic, sprayed grey, and laser engraved. The back panel is created from 3mm Clear acyrilic and painted around the edges to prevent light spill. These are combined with the lighting back box to provide a genuinely Awesome backlighted unit.
 
Based on the pictures, it seems like the back panel has been painted entirely in grey. It's important to note that the protective film needs to be peeled off upon receiving the parts. This will reveal the clear acyrilic to allow the light to pass through.