Explosion proof. It's a lighting fixture in a class 1 division 1 area. Everything has to be explosion proof meaning, the conduit and boxes can contain an explosion inside of the bodies without igniting the potentially explosive atmosphere that it is in. The conduits have seal offs to prevent the internal explosions from migrating through the whole electrical system and each box is machine fit which allows the gasses to escape from an internal explosion without igniting and/or blowing the stuff apart. It's all threaded rigid pipe.
The concern would be the material used for the
sign melting or burning because it is right on the light fixture. Every electrical component is UL and would assume that the
sign would also need a UL approval for that use.