An astonishing recent example (way beyond Tiffany) was that of a 2523 with the double-signature of a historic Italian AD, which technically made it "unique"....because of this, in Fall of 2019, the watch sold for over $8M.
Now think that this didn't bring any good luck to the AD, since earlier this month it suddenly (well, almost) lost its Patek license...So maybe the new owner will be able to resell that 2523 for $20M?