You might do a density test-- check on the web for info. You have to weigh it dry, then weigh it in water, and do a small calculation. The nice thing about a density test is it won't damage the item.
Another thing I do is look at it carefully under a loupe or microscope. Look for peeling (indicating a plated article) or corrosion (indicating a base metal). This won't be diagnostic unless it is obviously cheap junk.