There are a number of different ways to check weather a bar or coin is silver. A simple test is to use a strong magnet which are frequently refereed to as 'Rare Earth Magnets'. Since silver is not magnetic if you bring the magnet to the metal and the magnet ‘pulls’ towards the metal it is not silver. Silver also has a 'diamagnetic' property that you can test for. This property can be demonstrated by holding the bar or coin at a forty-five degree angel with a table and 'dropping' the magnet from a short distance onto the coin or bar. If the magnet slides down slowly(with resistance) as apposed to quickly it's probably silver. Silver also has an audible harmonic residence so when tapped while being held loosely a ‘ping’ will ring out as a posed to a dull thud.
As with gold there are silver test kits which have a dropper of acid and sometimes a test stone. Unlike gold, which has a few different test solutions, silver will only have one. Be careful with the testing solution! It is a corrosive acid. All directions should be read before using and gloves are recommended. Children under the age of eighteen should not use these tests. The test stone is for rubbing off a little streak for testing with solution or you can use the silver solution right on the silver. For sterling silver or higher fineness it will turn reddish. See the container for information indicating what dark and light reds indicate.
A scale is highly recommended. In expensive digital scale can easily be found. You might want to find one that has a “Troy Ounce” unit selection for easy conversions. Digital calipers can also be found and can be useful in verifying coins are within their mintage dimensions. Knowing the weight of your bar or coin you can use silver’s specific density (sometime called specific gravity) you can determine if it is true to its indicated fineness.
It seems like the bulk of counterfeit coins come from China and it is advisable to use trusted dealers only. When viewing listings be aware and avoid those with the labels of “mils or mills”. These refer the thickness of plating and not for the purity of the bar or coin. For an example; “1 troy ounce 100 mills .999 Fine silver dollar” is a 1 ozt dollar plated with 100 mills of 99.9% silver.