I have a bunch of them too. Four are in a counter I
made back in 73,
the rest are spares for it. Actually they are fairly nice and at about
10MA brighter than leds of the time (I must ahve a dozen MAN-x series
LED 7 segments as well).
FYI: those things are considered rare as hens teeth as most systems
that use them have burnt them out. One series of ARC (used in cessna
aircraft) radios had them as they were bright enough for day use
and I hear they cost about 100$+ per digit to replace.
I saw some at a hamfest. I lost my interest as I figured out that they
operated the same way as most VCR displays.
vax, 9000
Allison