copy and paste from my other reply:

Have you tested the metal with a magnet? The test is not conclusive, but it eliminates many silver colored metals. Hold up the necklace so it can swing freely. Using a strong magnet, approach the metal parts and see if there is any attraction. Some non silver metals will 'jump'. Others will slightly move toward the magnet. If there is any attraction at all, your metal is not sterling silver. It must be a STRONG magnet.

Another test is to polish with a silver polish cloth. If it won't come to a shine, it might not be sterling. Again, not conclusive, but can eliminate some candidates.

I don't know how to perform the acid test to further eliminate non sterling items. Maybe someone else can point the way.