For small silver items, you are much better off buying US 90% silver coins. If you later want to sell your gram silver bars, your buyer will have the same concerns you do. How do I know they are real...

Bags of US silver coins, 1964 and before, sell for about 21 times face. In quantity, a silver dime will sell for about $2.10. For daily prices, see:

https://online.kitco.com/bullion/completelist_USD.html

Kitco also sells silver items, but probably not less than a $1000 face bag. They do sell marked 1 T.O. and above bars, which should be OK as an investment as well.

You can also find smaller quantities of US silver coins on eBay. A roll of 50 dimes is a typical lot.

Few would try to counterfeit common US silver coins. Be sure to check the edge; it should be a uniform silver color. Clad coins will show the base metal layer in the center. Check that the date is 1964 or earlier.