Is there a reason any split-door OV-50 I've seen has a gold-ish looking rear door? Is it rust rust from inside? Every split-door OV-50 I've seen has the rear door discolored that way.

I loved these finned OV-50's. There's a few still in use in a Big Lots parking lot near me, that have been converted to metal halide.

Perhaps the door is steel and the rest is aluminum. They are a massive luminaire and weigh a ton. Not as pretty as the the big, buzzy, finned M1000's

That and the biggest disadvantage is the slipfitter will only take 2" pipe.

The 2"-only slipfitter is probably for the better... Most 1-1/4" arms aren't capable of supporting a fixture this heavy. I could see some dimwit trying to put one of these on a wimpy 1-1/4" aluminum pipe arm with no under-support or guy wire and the thing will ruin the arm (either it'll sag or the weld will fail where the thru-bolt flange is). These things weigh like 80 pounds. I heard the 1000W HPS versions with the big regulator ballasts weight around 100 pounds!

I have two M1000s. One is a 1000W MV and the other is HPS. The MV has the clamp/ring slipfitter that will go 1-1/4-2" and the two bolt rocker that will do the same.

They probably just used the same slipfitters used in the M-250 and M-400 lights of their time. GE used pretty much the same parts from luminaire to luminaire (which is convenient when restoring fixtures since you don't need to necessarily use parts from the same model fixture). Still, not sure I'd install any 1000W fixture on a 1-1/4" arm. It might hold up (with a steel arm) but for my own piece of mind I'd use 2" lol. Even 400W I'd use 2" though I see plenty of 1-1/4" arms holding 400W fixtures. Some hold up better than others. Depends what gauge pipe is used and if it's steel or aluminum. Almost all the arms here are aluminum.

I have a 6ft 2" diameter curved aluminum arm from National Grid. It's HAPCO branded. Never been used and made in 2015. Really nice rock solid arm. Would be perfect for a big ol' 400 or 1000W fixture, though NGrid even uses them for little 50W HPS M-250R2s, which is overkill in my opinion.

Here's my new HAPCO arm. I also found a NGrid roadkill aluminum pole with a 10ft truss arm. The welds joining the truss arm to the brackets that hold it to the pole failed, so I'll have to get new plates fabricated and welded onto the truss arm, which might be tricky since it's aluminum. No doubt it'll cost a fortune... A picture of that one is here.

I had a chance to have one of many finned 327's removed from a razed Kmart. Sucker was so friggin heavy i said forget it. Settled for a couple 250W wide-lite floods from the garden Dept.