Wow, amazed we missed this. Thanks for posting @nullcount.

As a few folks notes, the intention here isn't storing your whole stack in these. They're meant to complement BTC in cold storage. Our primary intent is that they are tools for gifting an education. Onboard a family member quickly with a beautiful piece that they can share. Show one off to a nocoiner and help them understand that Bitcoin is money.

We do not load notes, you do. We store an encrypted private key on each note (we generate the key) and you add a user key in plaintext. From those two you send the funds to a multisig generated in our app. We release the decryption key when you cut the note (we can authenticate that via the app). If we die or censor, the multisig downgrades to just the user key after Jan 3 2029. You can re-key notes that were loaded by untrusted parties. If you load less than face value, note scans as invalid. If you load more than face value, the remainder is used for fees during load.

The notes contain currency-grade security features in the printing (not that these really matter, it's all about the keys on the NFC chip -- but they look cool) and use a resilient synthetic paper.

Happy to answer any other questions here, or at @offlinecashco.