I have keys for those. I'll sell you one for a buck. You can e-mail me at handcufforg.at.spamex.com.
But personally, I wouldn't bother. You can probably twist them apart with a couple of big screwdrivers, or hacksaw the damn things apart. They're not worth the powder to blow them up. The key is probably worth more than the handcuffs.
I call them "Party Cuffs," but honestly, I don't even recommend them for that duty. They are complete dreck.