faceplate

noun

1. A removable protective shield separating the inner workings of a machine from operator and observer.

   “The keyboard's faceplate, that is, the cover holding the plastic key against the rubber keyboard, is usually molded ABS (acrylonitrile butadiene styrene) plastic.”

2. A rigid flat surface that has an active role in the interaction of a device with an operator or user.
3. A transparent window forming part of a helmet directly in front of the wearer's face, allowing them to see out.