Commercial canopy cab apparatus

[GA_Dave]

Do you know what the thing above the windshield is? It kind of looks like an AC unit, but an odd location and a rather rare option before fully enclosed cabs.

 

 

There is a lot of glare, but I believe it is a light bar installed in that position to clear a bay door that has a low clearance.

Yes, there is a lot of glare on that shot.  It was taken in the 1985-1986 timeframe, with an old 110 camera.  Not my best shot, but I never saw that rig again, either.  Hondok is correct, that is a Federal Twinsonic, mounted low to clear the station doorway.