It's a GUIDE spotlight, but it's a DUKW one rather than a Weasel one, functionally the same. I suppose I should add that my G-231 Iron Fireman T-36 has one too.
The Weasel / DUKW difference is quite obvious - it has a knob on the end :angel: DUKW unit has knob, Weasel one doesn't. The DUKW mount has a canvas strap with a ring that goes over the knob and holds the whole assembly in place which the Weasel doesn't need.
To use it you need the spotlight handle, or the remote handle mechanism that goes under the screen on the early Weasel. Late Weasel just has the ordinary handle to use it hand-held, with a special parking position just for the lamp left rear of the cargo compartment. T-36 has a special bracket to mount it front left in the cab, and the handle clamps separately to the left side of the dash. They also normally have a corrugated steel mask clipped onto the front edge, OD outside, black inside.
Handy thing to have on the shelf, not a huge value though, and I already have a couple plus brackets and mounts.
The bulb voltage would be 6v for the DUKW, and 12v for the Weasel and T-36, so the 24v bulb means it has been used on something else. I don't know anything WW2 that would've used 24v, maybe something Korean war era though. If it has the correct clear lens in it and the reflector is till in good order I vaguely remember you could unsolder the bulb bit and replace it in some of the configurations. I assume Rex Ward would have a new 6v bulb for it.
http://www.ebay.com/itm/WWII-Military-Spotlight-12V-DUKW-Sherman-Tank-Weasel-ect-/281866644716