How is it possible to store cryptocurrency on a non-electronic device such as a Ballet Cold Storage?

Cryptocurrency wallets do not actually store cryptocurrency. They store cryptographic private keys, which allow the owner to transfer cryptocurrency on the blockchain to a new address. So when we talk about ownership of cryptocurrency, we are actually referring to control of private keys. A private key is simply a long sequence of random letters and numbers, like a very strong password. Letters and numbers can be written in electronic and non-electronic form. Typical software and hardware wallets store private keys in electronic form on a device with electronic components. Ballet Cold Storage cards store private keys in two-factor physical form; the private key entropy is printed on a robust waterproof sticker and the passphrase entropy is laser-etched in steel. Ballet’s unique non-electronic design provides all the standard functions of every other cryptocurrency wallet but with greater physical durability and resilience than any electronic device.