How do you find out how much old coins are worth without getting ripped off?

If you have a substantial amount of coins, you should get them appraised. Some coin dealers routinely do this, for estates and insurance valuation/verification. since they are there to set the market value, and not purchase the coins, you should get a legitimate value.

Coins preserved in “flips”, for easy sorting, Identification, and storage.Flips and coin collecting supplies are Available on Amazon and eBay.