Hollow Spy Coins
Bruce Schneier's blog links to a few sources for hollow spy coins, one being BoingBoing's Bazaar — where a nickel that can hold a microSD card costs $27. Another is Slashdot's sister company ThinkGeek, where you can get hollow quarters and half-dollars in the low 20s. As if corporate and government security geeks didn't have enough to worry about.
I was a amateur magician when I was ten or twelve, and I'll be 58 next month. You could get those coins at any magic shop way back then, or through the mail from catalogs; I owned a couple of them. Also, any machinist can and could make them easily.
Free Martian Whores!