in the HeNe serie, here's the Karl-Zeiss LGR 7641

[shrad]

tube output power: 0.65mW
plasma sustain voltage: 1200V
plasma sustain current: 2 to 5 mA
plasma treshold voltage: 5000 to 6500 V

I got it lase with a 220V -> 880V transformer and a double alternance 8X parasitic multiplier with a 220K ohm ballast resistor

here are the pictures