Another easy way of determining the "authenticity" of various metals is to measure specific gravity of the material and compare with published empirical data. Steel has a specific gravity of 7.86 (7.86 x heavier than H2O) and Sterling Silver has a specific gravity of 10.4. This needs to be performed using a digital scale with part in question being weighed submerged in H2O and then weighed the normal way on top of the scale. If you are interested I can send you the details.
BTW - this will work for any material as long as it's heavier than water and you have empirical data on that material.
If you have a mass spectrometer laying around that would help also but would require damaging the part...
