Alusig Durasig Signals
Here is an 8 inch Alusig. Alusig heads are made of cast aluminum and Durasig heads are made of polycarbonate (plastic).
Here is an 8 inch Durasig head just like the Alusig.
Notice that the reflector assembly is very similar to the Alusig assembly.
Here is another 8 inch Durasig. This one has a reflector that is held to the door with the lens gasket. There is a groove in the lens gasket that holds the lens and the reflector to the door.
Here is a 12 inch Durasig signal
All of the signals shown here have thumb screws in the doors that hold the doors shut as shown here.