One of the advantages of Bitcoin is that even if it goes to 1 Million USD it will still be very affordable for people to buy. You can't say that about gold. Where would you store a small fraction of a dust speck of gold?
Gold foil in polycarbonate casing. This happens to be the scenario for currency money proposed by some goldbugs.
I'll take that instead of paper any day.
I'm sure by then everyone will have an ipad with a built-in electron microscope. I'm not sure how else you will be able to assay the gold.
A thin layer of gold is very visible and can be nearly arbitrarily thin, there is a saying like "One ducat, well malled covers steed and rider to the collar"
This can be either interpreted as the good malleability of gold or its value to pay a merc for a season. (One ducat is about 1/9 troy once)
A foil only about 10 atoms thin can be seen with the naked eye, and can be manufactured today without special effort. Validation would also be very easy since the optical properties of a layer of gold are very unique.