Original Atari smoked dark grey monitor glass. We have no idea what game this is for, it measures approximately 22 3/4" x 20 1/2" by 1/4" thick. We are fairly certain this was pulled from Atari classic game, we were thinking Tempest or a color vector game, but the dimensions don't seem quite right.
This is a glass bezel, overall in good condition, it does have a couple of minor scratches and wear spots. but should be fine for use on a game.