It appears to be an old-fashioned, relatively low power CRT display, presumably for radar. I believe these can't be guaranteed to produce a visible image in all

It appears to be an old-fashioned, relatively low power CRT display, presumably for radar. I believe these can't be guaranteed to produce a visible image in all cockpit conditions [1], so they mount a hood to block out peripheral light. [1] http://www.google.com/patents/US2819459 http://www.google.com/patents/US2819459