How Do You Acid Date a Dateless Buffalo Nickel?

By GovMint :

Acid dating a dateless Buffalo Nickel involves using a mild acid solution to restore the date that has worn away over time. This process works because the acid reacts with the metal where the date was originally stamped, revealing the numbers.This treatment can often bring back the date, making the coin more identifiable, though it does affect the coin's surface, can reduce its numismatic appeal, and is best left to the experts. 

Sources Used:

https://www.thesprucecrafts.com/no-date-buffalo-nickel-768849