The technique is muonic X-ray emission spectroscopy. Muons are subatomic particles which can penetrate metal to at least the thickness of coins. When muons interact with metal atoms, x-rays are produced that can be detected. The energy spectrum of the x-rays indicates which element is present. A muon beam can be played over a coin, and a map of metallic composition can be created. In addition, by adjusting the energy of the muon beam, different planes in the coin can be analyzed from surface to center. It’s essentially a CAT scan of the coin. Technique can be used for numismatic research on coin composition and also for counterfeit detection. Unlike XRF (x-ray fluorescence), it can go well beneath the surface … gold-plated tungsten would be immediately detected. And no, the coin is not damaged or made radioactive. The downside is that a particle accelerator is needed to produce the muon beam. These are very, very expensive. So for now, the technique will be primarily used for research. See the link. Cal https://phys.org/news/2021-11-muonic-x-ray-emission-spectroscopy-roman.html
Yeah, I don't think I'll be able to pick up a building-sized or campus-sized accelerator at surplus. On the other hand, there are some glimmers of hope for a desktop-sized source, based on some funky work that's been happening with laser-based electron accelerators (get giant-accelerator energy levels from a benchtop setup). I still don't think it'll be showing up at the local pawnshop in my lifetime, though. https://iopscience.iop.org/article/10.1088/1361-6587/aacdea
Wait a minute. I think I have one . . . somewhere around here. I'll have to look and get back to you.
I don't have one on hand, but... oh, wait, I do. Quite a few, in fact, since every CRT tube is exactly that. (They accelerate electrons toward a target, the screen.) Now, the giga-electron-volt energies you need to generate muons -- that requires equipment I don't currently have on hand. If I absolutely had to do it, I'd probably run up the tallest pole I could find, put a metal spike and heavy cable on it, and wait (literally) for lightning to strike.
