A 6914 is known as a Gen 0 image tube because it has no gain and converts shortwave IR to visible light. The photocathode is an S1 type and the screen a P31, both are 25mm indiameter. This Image Intensifer Tube requires about 15,000 volts at a few micro-amps for operation.

MH produces  Gen2+ night vision intensifier tubes to replace 6914 Varo Infrared Night Vision Image Intensifier Tube, Gen 2+, Inverted, Non autogated, 25 mm input and 25 mm output diameter, similar tube dimensions with Gen 0 Varo 6914

See the below physical picture,parameter and drawing:

Engineer Manager Name: Jacky