These marbles are what rattle when you shake spray paint cans, though some cans may have metal disks or ball bearings. Word has it that those marbles are commonly salvaged by Philadelphia (and other…) kids. Why buy things that are free in the trash?
To extract a marble: lay empty can on rags and newspaper…outdoors preferably…and wrap the bottom of can with a heavy rag. Use a sharp knife to stab sideways through the rag into the lower end of the can…like slicing off a half inch of salami. The can is still under pressure so leave knife inserted as a sort of valve to wiggle a little until the hiss stops. Rag will capture what leftover paint fizzles out. Use the knife to slice most of the bottom off the can. Leave a little hinge. Drip the little leftover paint onto rags. Then…voila!…dump out the marble, clean it up with a rag, and add to your collection. Recycle the can.
These marbles aren’t decoratively designed for the games market, but are nice iridescent glass, even with bubbles. With white paint on the back of a marble, the right light angle will produce an eerie reflection.