In the mid-60's when I was on merchant ships, many were old WW2 freighters and I kept noticing these slots at the bottom of each entrance hatch. I asked an old timer what they were and he said that during the war they contained 'glow plates' that emitted a dull glow at night so that the sailors could locate the entrance when the ship was steaming 'all lights out.'
Anyway, he went on to tell me that after the war many of the sailors took the 'glow plates' and made belt buckles, bracelets and necklaces out of them. Apparently a big problem as many people were burned from the radiation.
Radium plates..
along with all the guys that when blind several years after being on the radar array painting details.. (microwaving their eyeballs)