Need details on 35-year old Unisonic VFD (from a calculator)
To hack this, just identify the filament pins: measure with a VOM (not on ohms x1 scale, that might blow the filament) until you find two that are nearly shorted. Since you know what batteries were in the original calculator, the filament is likely to take 1.5v, maybe more (Google to see if there is any standard). Once you have a possible ID on that, feed it a controlled current (about 10-20 mA) in a dark place and watch closely for a fine line getting dull red as you increase the current. Don't go any higher, it's designed to run at sub-luminal temperature. If there is more than one pair that could be the filament, try all the permutations until you have it. (There is a slight chance that it is tapped, so three pins may connect to the filament.) Some pins may be simply shorted together and not go to the filament.
Once you have the filament, feed it a current just below the visible level, and while doing so connect about +15 volts through about 10K to each of the other pins and watch for segments that light up. Draw a diagram of which pin lights which segment.
After that, experiment with the segment voltage and resistance for adequate brightness.
It's a lot of work but it may be the only way to get this done.