I did this write up a few years ago.
https://www.vintage-radio.net/forum/...ad.php?t=88783
I find that using a 2.2v MES bulb provides a good bright white beam but the bulb soon burn out. So as a compromise I use a 2.5v MES bulb. Its not quite as bright or as white but the bulbs last much longer and the two C cell batteries last for ages. I still like to use it and often run it for a few hours in my workshop during the evenings whilst I am watching my old colour tv or just listening to one of my vintage radios. Its much kinder on the eye than the harsh 100w room light.