The SCiO can do that, I believe. Its not wide-spectrum so it can't fully analyze a big object at once, but it can analyze a spot on it. As you probably know, a spectrometer bounces light off of molecules / atoms and determines what they are based on the wavelengths coming back to the sensor.
I haven't messed around too much with generating my own data, but I do know that it can distinguish, say, real Advil over a fake.
Also, since we're dealing with light, metal's reflective properties might be an issue, but I'm not sure. I'll have to check and see if anyone has tried metal with it.
Can it tell you the molecular composition of a coin? Like zinc 2%, copper 20%, nickel 78% ?
In theory it should. Basically, when you start sampling a specific type of item it creates spectral charts. They anomalies in the charts that distinguish zinc from copper from nickel may be small so you may have to zoom in to observe them, but they should be there and you should be able to train the system to understand the difference.
I personally have only used existing apps with the device, I haven't tried coding anything yet with it or analyzing the data that comes from it. I would encourage you to check them out and ask them if you are that interested:
https://www.consumerphysics.com/