I recently stumbled across a newspaper article from 1995, completely by accident, talking about how the lights at my high school's football field were about to be replaced with MUSCO metal halides within the next year. This was a couple of years before I was born, and I don't have any pictures of the old fixtures, although I know I've seen one somewhere.

The original lights were installed in 1967, and were mounted on eight steel lattice towers. The article doesn't say what kind they were, so I'm trying to figure out if they were incandescent or 1,000W mercury vapors overdriven at 1,500W. The article does give some clues. It says the fixtures used 60 to 80 bulbs a year. While I know overdriving MV bulbs severely reduces their lifespans, I can't imagine high-powered incandescent bulbs would last long. It also said that the bulbs for the fixtures were no longer made, although they had bought enough replacements to last through the season. To me, this really screams incandescent. I'm pretty sure 1,000W mercury bulbs were still made in 1995, although probably not many. Does anyone know? It also says that the new lights were expected to save energy and provide better lighting. I interpret the last part to refer to CRI, but it doesn't elaborate.

I remember getting the impression that incandescent sports lighter fixtures were used well into the MV era because of the poor color rendering of MV bulbs. I know there were sports lighters that used 1,000W MV bulbs overdriven at 1,500W, but I'm pretty sure that HIDs didn't become common in sports lighters until the metal halide era. Does anyone know if this is correct?

Based on this information and the article, I get the impression that these lights were probably incandescent, but I wonder if anyone else may have an idea. Does anyone know what kind of ballfield light fixtures were common in the 1960s and what the lifespans of the bulbs were? Know of any bulbs that were discontinued around 1995?

Running 1000w mercury bulbs on 1500w ballasts was definitely a thing for lighting sports fields in the past. IIRC I believe Sylvania rated their 1000w MV lamps for a mere 2000 hours operating at 1500w compared to 24000 hours at 1000w. 1000w MV lamps were definitely made after 1995, I'm not sure about the past few years but they were definitely made into the LED era. I'd imagine overdriven MV would probably still last more than incandescent though.

My first guess after MV would be 1000w PS25 incandescent lamps in shovel style fixtures but I'm pretty sure even those were made after 1995. The timing of 1995 falls on the same period when the EPACT of 1995 became effective which saw several lamp types discoutinued. However the types I know of were fluorescent  and also lower power incandescent reflectors but it's possible higher power incandescent reflectors for sports fields were also discontinued.

A short summary of the lamp types discontinued are:
F40T12 40w halophosphate types (/CW, /WW, /D)
F96T12 75w halophosphate types (/CW, /WW, /D)
F96T12 HO 110w halophoshate types (/CW, /WW, /D)

R30 50w
R30 75w
R30 100w
R40 100w
R40 150w

PAR38 75w
PAR38 100w
PAR38 150w

I believe fluorescent lamps got energy saver halophosphate lamps at one alternative and full power 70+ CRI lamps as the other. Not sure about R30 and R40 lamps. The PAR38s got halogen replacements instead.

 

My experience as an electrician I'd say based on the original installation date of 1967, they were almost certainly 1000w mercury vapor overdriven on 1500w ballasts, especially how the article says they go through 60-80 lamps a year.
For a new installation in 1967, incandescent was outdated and overdriving 1000w mercury vapor lamps was commonly done as it more than doubles the lumens of each lamp though drastically reducing their lifespan.

Interesting. Do you know if all 1000W MV bulbs could be overdriven, or were there only specialized ones that were made for this? If so, could that have been what was discontinued around 1995?

Still trying to find a picture of the fixtures, FYI.

Update - here are some pictures. The first one is from the 1971 yearbook, and the second one is from the 1976 yearbook. They look a lot like https://www.lighting-gallery.net/gallery/displayimage.php?album=2473&pos=13&pid=67561 these fixtures or https://www.etsy.com/listing/4574426711/vtg-crouse-hinds-appleton-18-spotlight? this, although I can't tell for certain. I thought most of those fixtures were incandescent, although although https://www.historichouse.ca/antique-and-vintage-items/antique-and-vintage-lighting/other-lighting/vintage-flood-light/?srsltid=AU7gw4XyA5oyTbtrcrw44cSBkF8ut3weRWU0z9Gp_P4PZ0zG6ZiwXFAQ this one appears to have a mercury bulb. I also can't tell if they've got ballast boxes behind them or not; that dark spot in the 1971 photo about midway between the rows could be a remote-ballast box. Anyone have any ideas?

overdriving 1000w mercury vapor lamps was commonly done as it more than doubles the lumens of each lamp though drastically reducing their lifespan.

I wonder if there is a formula for this like with incandescents lol

There are, Here's a example for halogen lamps (page 8 ) but I suppose incandescent lamps are similar enough.

The fixtures do look more HID compared incandescent IMO. They might be using MV overdriven. If you want to read up more on this practice, it's mentioned in a old 1970s Sylvania engineering bulletin on page 18 under the section Overwattage Operation.