What Exactly IS “money”?

Gold is only good money if its weight and purity are
reliably authenticated.
X-ray fluorescence can reveal that Gold (Element 79) is
present in a sample, but will not disclose its exact
weight and purity.
The same is true for metal finding radar devices that
people use to scan the ground to get return signals
from metal pieces in the ground.
To reliably authenticate gold you need a tag of some
kind that exists side-by-side with the gold in an
enclosure that is sealed and tamper evident.
One example is a gold coin in a sealed plastic hold