I've seen a lot of the bucket style lights but I have two favorite models in particular. The GE Powrbracket, and similar style ones is the first. The second is the ITT version of it, there are still a few of these ITT lights in my area still in use, but a few have been replaced with more typical style bucket lights. However, I only know of two GE Powrbrackets in my area. The first I used to pass every day on my way to elementary school, and it was so different, I loved how it looked. I remember once we went to an evening festival at the school and I got to see it working on the way home. It had a green glow to the MV bulb and I liked that too. It is still there, I went down that road just this week and saw it, but unfortunately it wasn't working. The second Powrbracket I just discovered maybe a year or so ago. It is on a rural highway I rarely take, back off the road next to an old shed and the whole area around it is overgrown. I've also passed it at night and it too doesn't work.

The one next to the old shed likely does not have power going to it... bring a genny connect it up and let er rip! or if you feel up to it, and the light is abandoned you could always save it...

Here are some shots I took from Google Maps, sorry the pictures are big but it's hard to see them small.
I believe you are right on the one by the shed, you can even see the power lines from the transformer are on the ground. You can barely see the light, it's the white dot. I may pull over and get pictures sometime.

There's something quaint about these old lights, just hanging there, long forgotten amidst all the vines.

We had a 400w mv version, my dad put it on a 30 foot wood pole and stood it up at my grandparents farm, holy crap it could be seen for almost a 1 mile in any direction.

Here's one more I found that seems to be lighting a church picnic shelter:

It seems that all of the Powr/Brackets seem to be the 400W models, which I like the big reflectors best.

So I went to a yard sale this morning, and I got to the house, looked up and there was another Powr/bracket. Like all of the others I've seen, it had the big refractor and lens for 400w.
The street was kind of a cove that had three houses which may contribute to it's still being installed. So that makes at least three of these in my area.

These are fairly common in rural West Texas still, but not many left in the D/FW Metroplex. I Discovered one that I pass by every day recently. (Have made this drive now for 4 years and never notice.) It doesn't work anymore, which is the main reason I never noticed it. It either doesn't have a photocell anymore, or uses the older internal kind. I also have a brand new (old stock) unit that I bought from a surplus liquidator in Indiana last year.

That's a great find you had, especially since it was a surprise that it was complete with the refractor and 400W one at that. What a find for $40! I really like the 400W refractor, all of the ones here have that, and it's what I liked most as a child about them, though I only knew of the one back then near my school.