Odd mid 70s four lamp HO troffer at a local subway station. It's a 2X2 troffer with a rounded diffuser that normally covers the light. The lamps inside are Sylvania F24T12/CW/HO.
Note the shock hazard label on the dead lamp, the subway system uses those labels to mark failed fixtures and lamps.
My old middle school used to have bigger versions of this. I never really thought of them as troffers though becuase they didn't lay in the grid at my school. I never saw the inside, but they were T8 programmed start.
Yeah not sure why they do that sticker business, I've seen them on fixtures with dead ballasts too. I was a bit surprised to see HO lamps inside these too, I guess this was used to get more light per lume before PL 55 troffers were popular.
I've seen bigger circle fixtures too but I don't think they were HO.
Ay my old middle school, when the wrap lights had bad ballasts (and boy did it happen frequently in my computer tech room) they'd stick a red card of paper labeled BALLAST inside the diffuser, since when they change ballasts, they need to call in the school district electrician since each school doesn't have it's own apparently.
Kind of a late reply, but i've seen the district electrician before in 7th grade. he was replacing a duplex receptacle while my english class was in the auditorium doing a play (no audience, we just did a portion of Harper Lee's To Kill a Mockingbird in groups with our class). We were in the way apparently and boy was he a jerk.
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I've seen bigger circle fixtures too but I don't think they were HO.