It is often possible to sort various alloys of a nonmagnetic metal by means of an eddy current test when:

There is a unique range of permeability values for each alloy.

There is a unique range of conductivity values for each alloy.

The direction of induced eddy currents varies for each alloy.

The magnetic domains for each alloy are different.

The alloy is slightly magnetic, but not if totally nonmagnetic.