This thread reminded me of something. In Soldier2000 or earlier kit there was some kind of light SBS/SAS used. There didn't seem to be much info about it online but some were for sale on Ebay UK back in 2018. They were these radioactive lights that were used for reading maps. Very low light level and I think classified but definately had an NSN but still that can sometimes be rather vague. I assume it was tritium but I don't know. Was priced too high for me to buy too.