Very cool. 😎
I could do with one of those.
I like the idea of stamping on standard washers, rather than plates.
Discussion
It’s slow going, but cheap and reliable. You can down the jig to 3D print yourself. Then the washers can be bundled into a tube with a bolt and nut. Very compact for storage.
Not my idea, but I wrote about it here. https://briangreen.net/crypto_seed_backup