Energy-dispersive x-ray spectroscopy (EDS).

Energy-dispersive spectroscopy (EDS) allows forensic scientists to determine which elements are present near the surface of a sample of interest and also in what approximate ratio these elements occur. This method is extremely useful for the comparison of two pieces of evidence to see if they are consistent with each other. For example, two coins, one known to be ancient and one purported to be ancient, might be compared to determine whether the second coin is a fake. EDS reveals whether the metals present in the two coins are the same or different, as well as the proportions of the metals in each coin; if the metals or their proportions are significantly different between the two coins, it may be concluded that the second coin is a fake.