Do Pure Silver Coins Have Other Metals in Them?

By GovMint :

Even 99.9% fine and 99.99% fine pure silver coins usually include small amounts of other metals like copper. This alloy composition actually enhances the coin's durability and resistance to wear, which is particularly important for coins that are handled frequently. When silver coinage circulated in the United States, its composition used to be 90% silver, 10% copper, which was necessary to keep the coins from degrading too much over time. 

Sources Used:

https://www.investopedia.com/terms/b/bullion.asp