The jug sure looks soft especially the red. If the G-2 & heater check out we can give you a cheat. I dont think its a Zenith EFL, IIRC NAP never used it.
Between NAP, RCA / Thompson & Zenith they built almost all US tubes
and many for JA & Korean sets. May be one reason neither had EFL's.
73 Zeno
LFOD !