When it comes to jewellery, I check for markings with a little magnifier I carry in my bag which I bought on one of my last flea market visits and it's been great so far to check if I was dealing with actual silver jewellery.

It's really difficult and a lot trickier than one might think. Everybody talks about the magnet trick. For instance, a silver quarter and copper coins both move with the magnet test, so the magnet test alone is not conclusive.
With the "Ring" or "Ping" test, you can hear the difference, but you have to be in your game to hear it. The other is the "Drop" test. For silverware and jewelry, unfortunately, you've got to know your markings. An example would be a lion with its foot in the air which is the mark of sterling silver, or the word "sterling" or "ster", or the numbers "92.5" or "925", chances are it is silver. Buying silver requires knowledge of the years and marks (hallmarks) of silver.

Another way is using the Acid test. Watch the video.

For coins and silver bars, you would like to weigh it. Precious metals are typically weighed in troy ounces and pounds. You will need a high quality weighing scale. It does not weigh right, it will save you a lot of testing. Next, check the dimensions of the coin. You will need a digital caliper. The diameter and the thickness of the coins need to be checked. In coins, the weight, diameter, and thickness are usually good indicators of whether they are fake or not. Coins are defined by their size, weight, and dimensions. Then you can do a ping test. And you can use an earth magnet (the magnet will just slide slowly on the coin's surface if it's real silver). Last, you can use a "Sigma Metalytics" or a Precious Metal Verifier (which I do not have).

!BBH