Mine uses 5V on the filament and 12V on the grids and segments. It's a 12 digit display from an old calculator. The glow is beautiful, I really must find some application for it.
To find the filament measure between all pins in sequence until you find a pair with a fairly low resistance, connect a variable supply, ramp up the voltage from 0 until you see a slight glow. Back off until it doesn't glow but stays hot. That's the filament voltage. The filament is also the common electrode for all the rest. Which goes where can be determined by systematic trial and error.