Electrical metal tester

We have two we use at the store.

But the only benefit I can see is that it is non-destructive.-That
is, you don’t have to scratch the piece you are testing as with a
typical acid test. I have found that it errs on some gold pieces from
Mexico, as well as Italy, when I have double checked the machine with
a traditional scratch test, and found it was being very generous as
to the gold content of certain pieces. If people are giving you the
pieces and it doesn’t matter if you scratch them, then save your
money and do your testing with a traditional acid test, just remember
that the acid does have a shelf life once it has been opened.