Copper FTW!
Commercially available etchants, and resists corrosion for centuries / millenia. And not too expensive.
Discussion
Any links to what you mean?
Regarding etching, any electronics hobby store should be able to sell you printable etch-resist transfer sheets, and ferric chloride etchant. You can get pure copper sheet at metal fabrication suppliers, or ebay.
Then you can use a computer to put your 12 words into a printable and possibly artistic / obscure design; print this on the transfer sheet, iron the transfer sheet onto the copper sheet, and dunk the sheet and etchant into a dish for ten minutes.
Beautiful, high-resolution result, and the copper sheet will last practically forever, even in the ground. Archeologists dig up well-preserved copper artifacts all the time after thousands of years.
Sounds pretty cool. Maybe BTC Sessions could give a tutorial. nostr:nprofile1qqspnzgrfett3asxcuj0gksje6z2zxzpvgd27uvz58m9vsuqh8zzw6cpr9mhxw309a382emdv9hzumt8w4ujumn9wsargwp58qq3vamnwvaz7tmzv46xztnwdaehgunfdshxxctdqydhwumn8ghj7en9v4j8xtnwdaehgu3wvfskuep0w3hku7gpewmsc