Ballet wallet can not really be considered a hardware wallet, it's more like collectibles item, and it is not secure enough to be good cold wallet, despite what developers are saying.
Someone else generated private keys and they know about them, so you need to trust them and everyone in manufacturing chain... that is a lot of weak points.
If you like card format for hardware wallets, there are better options you can explore, some of them are even open source.

The encrypted private key can only be decrypted by the user-created passphrase. This is a trustless, two-factor security design based on the Bitcoin BIP38 open-source standard. The process utilizes advanced cryptography but the complexity is hidden from the user. You only need to follow a few basic steps. First, create a passphrase and use an open-source software tool to generate a BIP38 intermediate code. Then send the intermediate code to us and we manufacture a wallet with an encrypted private key that can only be decrypted by the passphrase you used to generate the intermediate code. A BIP38 confirmation code is engraved on each wallet so you can cryptographically verify that the encrypted private key can actually be decrypted by your passphrase.