We've got a ton here the IT guys use for fiber, but I'd never really looked all that closely, I just assumed it was plenum-rated ENT, as orange generally indicates plenum and it sure looks like ENT. You're right that the writing is illegible, it's insane...

I think I can make out:
CONDUIT 1" PLENUM CORRUGATED (ETL) UL ####

...but I can't read the UL #.