How do you get a fair price for old coins when you don’t know what they’re worth? That was the question my father-in-law, Howard, and I faced last summer. He had a pile of change inherited decades ago: a 50-cent piece from 1826, a penny minted during the Civil War, a silver dollar from 1885 and six more from the 1920s. I had a $2 bill from the 1950s and some pristine John F. Kennedy half-dollars from 1964, the last year the U.S. minted silver coins for circulation.