As promised, sorry for the late reply, I have been a little busy.
Your project reminds on one similar idea made by 21e15.com, but I think they are using even smaller size letters.
It's amazing to see that just a single washer can be used to store all 12 or 24 seed words.
Another thing I like is the fact they are offering titanium and standard Stainless Steel washers.
Size they are using for washers is very similar to coin shape, but I think their kits are a bit more expensive.
One downside of this strategy can be for people with bad eyesight, but it's easy to use glasses or magnifying glass.
https://www.21e15.com/