ca. 8mm symbol tube manufactured by National Electronics

The NL-911 is a clear glass symbold nixie tube manufactured by National Electronic. It has two independant stacks of characters. The right side can display "V", "S" and "A". The left side displays "µ", but also shows mechanicals for "N" and "M", sadly these did not turned on. I'm not sure if they are really connected to the pins. I also have absolutely no information about this tube. By the displaying characters i guess this tube was used in measurement devices for Ampere,Voltage and Siemens. Any Information about this tube would be great!
Brand / Manfacturer National Electronics
Same Types
Likely Tyes
Symbol height in mm ca. 8
Characters / Symbols µ,A,S,V,(M,N)
Decimal point none
Base / Socket unknown
Starting Voltage (typ) tested at 170V, 15kOhm V
Maintaining Voltage (typ) 0 V
Current per Segment 0mA
Reccomend Resistor 0