In the United States, a significant number of private mints produce bullion which is not legal tender and is targeted at investors and not at coin collectors. Most of these are in sizes based on the troy ounce, but some are metric - such as the one hundred grams (100 g) of silver.
This type of silver round has been produced since 2014.
The Mint says about it:
This Scottsdale Mint original Stacker Round is 100 grams (3.215 Troy Oz). It stacks and interlocks with the other two sizes - the five ounces and the two ounces, which have the same diameter. With Ultra High relief definition it’s not exactly a coin or a bar, it is truly a new class of precious metal.