Mint Mark
This is located on the reverse of the quarter below the wreath. If there is a D the coin was minted in Denver, an S is for San Francisco and no mint mark means the coin was minted in Philadelphia. There were about 36 million 1940 quarters minted in Philadelphia, 3 million in Denver and 8 million in San Francisco, so the last two carry premium prices.
Lower Grades
The lower grades for the 1940 quarter are as follows: F-12 (fine), hair lines above Washington's ear and feathers on the eagle's breast barely visible and VF-20 (very fine), wing feathers and most hair details clear. Prices do not change much from year to year so estimates for values for these grades by place of minting is $2 to $3 for Philadelphia, $10 to $15 for Denver and $5 to $7 for San Francisco.
Extremely Fine
This is known as EF-40. Washington's hair lines must be sharp, with few wear spots on the coin. In this grade the values are $4 for Philadelphia, $24 for Denver and $9 for San Francisco.
Uncirculated
Also known as MS-60, the quarter must have no trace of wear, but is allowed some contact marks and surface spotting. Values for this hard-to-find grade are $17 for Philadelphia, $120 for Denver and $21 for San Francisco.
Gem Uncirculated
Shortened as MS-65, this quarter must be immaculate. Prices are $60 for Philadelphia, $325 for Denver and $65 for San Francisco.