My father has that exact arm at his house but with a incandescent admiral hat light on it which has been sitting in the garage for 5 years. Once I finish wiring his garage, he's gonna give it to me.
Are you going to try to restore it? the arm probably wasn't origionally painted, but it will come out nice with a good sanding and a fesh coat of paint. Where did you dad get the light and arm?
Those Holophane Mongoose roadway luminaires are taking over where I live. Almost all of the new road construction projects going on here, they are installing these Mongoose luminaires. Probably cause they are cheaper to install. With these you don't have to install them on a mast arm. They can just go right on top of the pole itself.
Only these were from wwII era and were made by GE, they were originally MV but were converted to house hold incan, they were on buildings in this cute little tourist trap of a town with a population of 18!