Since we have the seed word metal backup covered wouldn’t it be nice to be able to backup your BIP39 passphrase(s) as well on a piece of meta that lasts a very long time and is resistant to fire and flood ?
The fact that we were offering a product that let you stamp your seed words and store safely but there was no way to actually do the same with the passphrase bothered me greatly. Coldbit Steel has an additional line at the bottom:
That line in theory could be used for stamping the passphrase but in practice it’s a very bad idea to store the passphrase together with the seed and I advise anyone to NOT DO THAT. Instead this line can be used to label your wallet (useful if you have multiple hardware wallets and thus seeds), say eg. “TREZOR A” or “LEDGER B” etc.
Because, unlike the seed, the passphrases change fairly often so I wanted to be able to store more than just one passphrase and decided to use a stainless steel hex rod. A hex rod has 6 sides which means you can store up to 6 different passphrases. It’s 10 cm (4”) long and will fit a maximum of ~ 28 characters per side.
The hexagonal rod form and small size allows for creative ways to hide it in your house or the area where you live. For example you can drill a hole in your door frame and hide it there (you need a 16mm (0.63”) drill.
IMPORTANT: Never store the passphrase rod together with your seed backup. It should be kept in a different location.
I don’t know of anyone else offering a passphrase metal backup. If you do know please let me know in the comments.