Further to our conversation the other day about Coldcard and sd cards and passphrase file stored on the sd I found this in the documentation

SAVED PASSPHRASES#

Passphrase values are stored in the /.tmp.tmp file on the microSD card. The values are encrypted with AES-256 (CTR mode) using a key derived from the seed words and a hash of the microSD card's unique serial number, restricting the file to the specific card. You cannot copy the encrypted file to another card.

Optional: microSD card (up to 32 GB capacity, FAT32 or FAT12 format) for saving the passphrase

nostr:npub1yx6pjypd4r7qh2gysjhvjd9l2km6hnm4amdnjyjw3467fy05rf0qfp7kza nostr:npub12r0yjt8723ey2r035qtklhmdj90f0j6an7xnan8005jl7z5gw80qat9qrx nostr:npub1lhezms58jx4yer60y3wzldc83fdez3j4rc4ue3edhz5qv3wxfsgqhhw94n