A few interesting (perhaps) tidbits of nerdery:
1:
> "But when Dr. Ortega and Ms. Bravo Hualpa bombarded the 1899 coin with X-rays and measured the light it re-emitted, they determined that the dinero was largely made of copper, zinc and nickel.
This sounds extremely fancy (and technically it is), but what you may find surprising is that the technique they used (XRF eg X-Ray Fluorescence analysis) is so useful in the coin/bullion industry that you can buy handheld "XRF guns" that perform a metal composition analysis on the spot and present the readout in a very easy-to-consume way on a small LCD screen. And you can buy them on Amazon!
https://www.amazon.com/XRF/s?k=XRF
(They are not cheap.) But they are ridiculously useful and it feels like a magic trick to point it at a piece of metal and have an instant elemental readout. As you might guess, 99% of this is to check whether a piece of gold/silver is actually gold/silver.
2:
Unlike TFA's example, among US coins there are lots of counterfeits out there that ARE made out of the proper base metal (typically 90% gold, as much US gold coinage is composed).
Why on earth would someone do that? The answer is that in the mid-20th century, many countries (including the US) imposed restrictions on import and export of gold but had exclusions for certain types of currency. So one clever way to transport quantities of foreign gold into the United States was to make sure you were transporting exempted US currency. So many countries developed sophisticated counterfeiting techniques to turn non-US-coinage gold into US-coinage gold. This worked quite well for getting gold into the US but has been a thorn in the side of collectors here for a while, since you might buy a rare US gold coin that's actually truly made of gold and yet is still a counterfeit :(