Here are a couple of pictures showing the old high-bay fixtures in my high school's gym that I took from a couple of old yearbooks. This gym was completed in 1966, and I'm pretty sure these are the original fixtures (the oldest photo is from 1975 or '76). I the first one you can clearly see what looks like ballast boxes and steel electrical conduit connecting to the fixtures. These fixtures were late replaced with 400W metal halides, probably in the 1990s.

I assume these were mercury vapor fixtures, but I don't know. Can anyone identify the make and/or model, or know of pictures of similar fixtures on this forum or elsewhere?

I was born after the peak MV era, but I distinctly remember when 400W MH was the most common gym light fixture. Were MV high bays commonly used in gyms before the MH era, and if so, what was the wattage? If not, what was common? I'm guessing 400W MH indoor high bays became common in the 1980s, and probably replaced similar 1000W MV fixtures, but I don't know.