The Form 109 here is still in excellent condition overall save for corrosion on certain steel parts which can be fixed, and I plan to fix that when I have time. The Form 109 was GE's first streetlight luminaire that uses the lamp in horizontal orientation; introduced in 1948. At that time the H-1 mercury lamp was still in heavy use, and since these lamps can't be operated reliably if not operated vertically, the Form 109 often came with electromagntic coils to keep the arc stream in control which permits the H-1 to be operated horizontally. This particular 109 was made in the early to mid 1950s, but still has the coil in the head!
The lamp is a Westinghouse 400 watt BT-37 DX, circa mid to late 1970s. Note that the lamp socket is in reverse position rather than the forward position. The Form 109 is in fact sometimes called the Form 109 "Reverse" because of this orientation.
You can see the electromagnetic coil in the head above the lamp and reflector. The coil's varnish coating has worn out, and the metal strip holding the coil has broken from corrosion on the left side.
