The idea is inspired from econoalchemist's blog post Securing a Bitcoin seed phrase in stainless-steel washers. and it's very great:

• Materials cost under 5 bucks (€, $, £, it's always the same ballpark). I paid around 3€ for 32 washers and maybe 1€ for the screw and nut.
• No shipping cost since everyone has a hardware store nearby.
• Anonymous since nobody knows what you use basic metal hardware for.
• All stainless steel, quite durable, on par with commercial Bitcoin backup products.
• Greater thickness than some commercial products

Backstory:
After reading the aforementioned blog post, I went to download the file for the jig from blockmic. It can be found in their Thingiverse and they wrote a very good article about it.

But: For one, I wanted to use larger washers. In fact, I think I got the largest that I could find in the first hardware store I walked into. A reason for this is that larger washers are usually also thicker and thus more durable, and the other reason is simply because the stamps I already had were too large for such small washers.

I have 6mm high letters and the stamps are 9x9mm in size.

So I did the natural thing: create a new 3D design from scratch, which is completely parametrized. This allows me to adapt it for anyone with different sized washers and / or stamps! Then did a few iterations, as shown here, and now it's ready to rock!




PSA: I can achieve much better print quality than what you see in the images, but I am finishing up some old rolls which have taken a lot of humidity so the results don't look as good. Also, I used more perimeters than CryptoCloaks since it makes things more sturdy. Finally, the darker colour you use, the more print lines show (especially when photographed)