The 1964 quarters start at a value of $5.14 each. They are higher priced than their value, because of their high content of silver in the old quarters. The condition of the quarter and which mint produced the quarter also change the value of the quarters. Two mints struck Washington quarters in 1964, Philadelphia and Denver. Those minted in Philadelphia are worth a small premium today. You can tell them apart by the small "D" placed on the reverse by the Denver Mint.
The next challenge is determining the condition of the quarter. Commonly found worn, look to see if the coin is in a higher more collectible "Uncirculated" condition, and compare it to "Grading" images. A popular series with collectors and elusive in the higher grades, the 1964 quarter is worth a close examination. There are places one can look online to find grading images and more information on what to look for in a 1964 quarter or earlier quarter.