definitely for making divers weights for their weight belt as about 15 people have stated and know cause they probably used them Marketers got into the diving world in the early 80,s i believe. That is when all the coated lead weights in different colors started.. And only the old schools divers cast their own, or just picked up brand new gear that the newbies had lost . Tanks used to be steel and 72 cubic feet of air , when pumped to the labeled psi, bit most of the wreck divers would overfill them and replace the Buiron disk, as crazy as it was. Wet suits were black, nothing else. We made pony's out of O2 tanks . Marketers got in and took over and came out with all there money schemes like deep diver masterbat diver, diivemaster, with zero open water no hand held dives, you could buy an instructors card for a couple thousand, be a certified instructor and never had made any real dives. lot of people died in the 80's , mostly instructors, diving in the area i dove which was off NY and NJ no idea on what the industry is like now, but i was fortunate enough to learn from the ships were wood and men were iron days.. The good thing is they got 1000% better safety with mixed gas , i am sure at a very steep price. I thought it was south Hampton NY at first reading, a lot of the tropical fish would be very close to shore in October as the gulf stream moved up, People would fill their salt water aquariums, Even off shore on the wrecks i would see angel fish and other tropicals, Doing an hour plus hang after a deep dive on air for deco and having a pilot fish for company was always interesting.