There was some nuance to the question that sort of took it in a particular direction.
The discussion started after someone posted a picture of a cool bolt/wingnut/washer mnemonic device. And the question was how long would it take to put 24 (or 12) words into the right order.
12 vs 24 from the dictionary of 4096 words? Both quite secure. But if you had the 12 washers and did not know the order, doable with enough CPU power to run the permutations. 24? Not so much.
So I think we were talking about different parts of the elephant.
Ahh yes.. if anyone has physical access to your bolt and nut, you're probably almost screwed, especially if they have not yet disassembled the device. If they were stupid enough to unlock the nut and spill out the washers randomly, then you have some time to move the coins (assuming that was not your only copy of the seed phrase).
a 24 word seed. on two bolts.
brass washers numbered 1 - 12 using 12 seed words of 24
aluminum washers number 1-12. using 12 seed words of 24
stored in two places.
if an evil doer finds the brass ones he will think he has a 12 word set of a seed and go no where.
if a second evil doer finds the aluminum ones he will think he has a 12 word set of a seed and go no where.
so an evil doer needs to find both and then figure it is a 24 seed wallet not a pair of separate 12 seed wallets
but what if i find both my brass 1-12 and my aluminum 1-12
well a comes first so list the 12 aluminum then list the 12 brass.
Since we are talking about this, and some of us (ME!) are kinda tweaky and like yefi said entropy junkies etc... I have some suggestions maybe already made.
1. Do not use aluminum. Aluminum melts somewhere just north of 600c which is a bad fire is going to be reached. In a bank vault you are likely fairly safe? But why risk it. Use Brass and Stainless Steel, or Titanium. I would say the latter two, but I think you are going for a color difference.
2. Use a BIP-39 passphrase. This cannot be stressed enough. This is the second layer of protection, that is absolutely needed! And this is true for all setups IMHO. All the various hardware wallet cracks using lasers etc? Only good for getting the seed. The password has to be brute forced. So even a fairly simple password, or pass phrase will add a significant amount of entropy.
Bonus: Using the BIP-39 passphrase gives us a cool trick we can play. Say you are fortunate enough to own 10 bitcoin. Well I would do this: Put 1.x BTC in an address derived from ONLY the root seed words, and then the rest (8.x) in an address derived from the seed + password. This gives you a way to "hand over all your bitcoin" if you were threatened without losing everything for real.