Looks like a GE Powr/Bracket fixture, or at least a complete copycat of one. The optical assembly looks different to me though. Definitely wasn't originally like that...

This one is a Westinghouse, the precursor to the (now Cooper) Vanguard ballast-in-arm fixture.

Oops, mistaken for this one . I typed too fast...

I think you're right on both accounts.

Wow, I thought the lenses on these were bigger. How is this not melted?

the 400W units are indeed supposed to have a bigger refractor. The original must've been damaged or went missing so they jury rigged this refractor. I can see this refractor is a tad yellow, meaning it's polycarbonate, so it could melt but not as likely to as acrylic (well, acrylic definitely would have at least deformed from the heat of 400W) but I guess this didn't operate long after the lens was installed since I'd expect it to be cocacola brown after years of a 400W lamp beaming 2" away lol.

This is a Canadian General Electric Powr/Bracket fixture.It originally had a 16"refractor,you can see the rivet holes where the clips used to be,that is a 12" Westinghouse refractor,the shield was common with late 60's early 70's Westy brackets.

Interesting they modded it for a Westy refractor lol.

Yeah lol.