here's a crazy turn of events. still plastic but they have something inside them.
this is only something written--me thinks there has got to be a link to metal commerative issue.
here's the link but i've quoted what is said...
http://s2.zetaboards.com/KoreanMusicRealm/topic/663167/1/
"This happened after i watched the American version of 'The Ring'.
I got home and I started playing korean jacks (gong gi) and I somehow
managed to lose one under my bed (which was against the wall). I felt
too lazy to go retrieve it so I left it alone.
It was finally time for bed, so I turned off the lights and turned on my
mp3 player since I usually listen to music before I end up falling asleep.
I suddenly woke up in the middle of the night, and everyone else in
the household was sleeping. So I lie there trying to go back to sleep.
Then I hear this weird sound on the floor under my bed. And I realized
it sounded like my jack piece (for those of you who dont know, Korean
jacks are usually filled with rice grains or little metal pieces, so they
make this little sound when you throw them around). I was already
freaked out from the movie 'cause ya know, I cant watch scary movies!
OH MY GAWD, I threw the blanket over my head and blasted my music."