no need for fancy. buy 13 large ss washers from local hardware store. punch your mnemonic, stack in order (but also # them), then put a bolt through them.
Keep it secret...keep it safe.
Discussion
At the same hardware store you can buy a set of letter punches and a fat hammer. If you're feeling sassy, buy a blockmit as a hammering guide.
oh, that's handy
Thanks! Your lightning address doesn't seem to work, I couldn't zap you.
Looks like you figured it out. You can get a blockmit jig here. Make sure you size the washers appropriately
https://www.amazon.com/Blockmit-Washer-Jig-Security-Fireproof/dp/B0D96MM5B9?th=1&psc=1