1940 makes it a Walking Liberty half, so the mint mark is on the reverse (tails) side, directly below the leaves of the branch, to the left of the word "half." D is Denver, S is San Francisco, and no mark is Philadelphia.
The mint mark on a Barber Half Dollar is located on the reverse side right under the tail of the eagle.
The 1920 Half Dollar - aka - Liberty Walking - mint mark of "D" or "S" would be located on the reverse side, just to the left and above the "H" in half dollar.
The mint mark on Franklin half dollars is on the reverse side, just above the Liberty Bell.
All average circulated Liberty Walking Half Dollars dated from 1940 to 1947 regardless of mint mark have the same retail value of $15.00-$25.00.
The mint mark on a 1936 Walking Liberty half dollar is located on the reverse [tails] side of the coin in the little "valley" just to the left of the word "HALF" near the edge of the rim.
The first Half dollar with any mint mark was from the New Orleans Mint in 1838.The mint mark is on the reverse under the eagle
The mint mark on a Barber Half Dollar is located on the reverse side right under the tail of the eagle.
The mint mark is on the reverse of the coin between the tail and the D in the word dollar.
All average circulated Liberty Walking Half Dollars dated from 1940 to 1947 regardless of mint mark have the same retail value of $15.00-$16.00.
No mint mark indicates that the coin was minted in Philadelphia.
The 1920 Half Dollar - aka - Liberty Walking - mint mark of "D" or "S" would be located on the reverse side, just to the left and above the "H" in half dollar.
The mint mark on Franklin half dollars is on the reverse side, just above the Liberty Bell.
All average circulated Liberty Walking Half Dollars dated from 1940 to 1947 regardless of mint mark have the same retail value of $15.00-$25.00.
No, 234,308,000 were struck at the Philadelphia Mint and will not have mintmarks.
The mint mark on a 1936 Walking Liberty half dollar is located on the reverse [tails] side of the coin in the little "valley" just to the left of the word "HALF" near the edge of the rim.
All average circulated Liberty Walking Half Dollars dated from 1940 to 1947 regardless of mint mark have the same retail value of $15.00-$16.00.
Not being certain which half dollar you have, I can tell you that there was never an "A" or a "N" mint mark. The letters you should find will be a "D", an "S", an "O", a "P" or a "CC"