Because physicists couldn't see anything so small as an atom, they had to try to work out its structure from how it behaved when they did things to it, as Rutherford had done by firing alpha particles at foil.
Gold items were found at the Sanxingdui Ruins site as early as 1986, including gold foil pieces that show how the precious metal was used by the ancient Shu people.
All we can say for sure is that this delicate sliver of burnished gold with its Phoenix-like dancing birds is lasting testimony to a very important fact.
That gold leaf was applied somewhere between the seventeenth and nineteenth centuries, when ancient pots were being discovered, collected and displayed by Japanese scholars.