Title: "Each Casascius Bitcoin is a collectible coin backed by real Bitcoins embedded inside.  They come in two denominations: 1 bitcoin, and 25 bitcoins.  Each piece has its own Bitcoin address and a redeemable "private key" on the inside, underneath the hologram."<p>One big weakness is they seem to be "single use" though, as they need to be torn open to be used.
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