The Dremel/Chromium thing is cool,
But I would go lower tech than that if I wanted it to last 100 Years..
Use the paper backup from Armory, that will (should) always work.
Use a Credit Card Size Plaque made of Stainless Steel.
Punch The number set in using an Alphabetic Punch Set
like This;
http://www.sunsetcrystals.com.au/metal-punch-stamping-sets-4mm/http://www.sunsetcrystals.com.au/images/P/uppercase%20basic%20stamp%20set%20-%204mm-2.jpgNail it to the underside of your house, or somewhere that no one is going to be passing regularly.
Make it somewhere you could easily describe to someone, like if you are in an ambulance.
Possibly make a wooden sleeve for it, so its not obvious, or possibly fold in half, so it can't be read by just glancing at it.
The code requires no password, so take care where you put it.
You could cryptically remove or reorganise, but to me, thats asking for trouble.
And obviously TEST THE RESTORE before putting it away and forgetting it.