Price guides for old coins are available online at PCGS.com and NGCCoin.com, as of 2015. The websites deal in all the American coin currency minted since the late 1700s. The price guides use special criteria to judge the condition of coins.
The Numismatic Guaranty Corporation and the Professional Coin Grading Service have guides for the flowing hair dollar, the liberty cap half cent and the bust half dime, all of which come from the mid-1790s.
Both websites split the grading into mint or proof, which is the initial first grading criterion and affects a coin's value greatly. Beyond mint and proof, the websites organize coin condition based on a numerical value, and coins in the best condition take a 70 rating.