Cool! The six Lithonia 350W PSMH highbays I removed from the Aerovox capacitor building in New Bedford, MA were labeled 277V-Only but actually had quad tap Advance ballasts inside. I kept the ballasts and put them in my Holophane Prismalume glass highbays, which were originally 400W probe start MH but converted to 350W PSMH with 277V single tap ballasts.

Usually when the label only lists one voltage, even though it includes a multitap ballast, is because it comes pre-wired from the factory and ready for connection to the specified voltage.

That was the case with the Aerovox highbays. They came with cord whips and modular plugs on them. They left the unused voltage taps tucked in the ballast compartment. You literally have to take apart the whole light to get to them. For some reason they didn't leave them rolled up in the wiring compartment.