What is the value of a 1943 Mercury dime?

1943 is not a rare date for Mercury dimes. First, check the back next to the Word ONE to see if there's a mint mark letter. It may not have one, or there may be a D or S.

In lower grades the coin is worth roughly its silver melt value, about 0.072 times the current price of silver.

The only 1943 dimes to have extra values as collectibles are in almost uncirculated or better condition. Numismedia lists the following approximate retail values as of 08/2011:

No mint mark:

Uncirculated - $6 (MS60) to $475 (MS68)

"D" mint mark:

Uncirculated - $6 (MS60) to $90 (MS67)

Almost uncirculated - $3

Uncirculated - $7 (MS60) to $96 (MS67)

Why "Mercury"?Technically they're called Liberty Head dimes but they almost immediately got the nickname "Mercury" dimes because Miss Liberty's winged cap looks similar to the one worn by the Greek god Mercury. The W "mint mark"Many people are confused by the W on the front of the coin. It's actually an intertwined AW, and is the monogram of the coin's designer A. A. Weinman. Prior to 1968 most US Coins had their mint marks located on the reverse side, and Mercury dimes are no exception.
So many Mercury dimes were made from 1940 to 1945 regardless of date or any mintmarks that most are only valued for the silver, about $2.00.
That's a MERCURY dime, not Neptune, though the image is actually of Liberty. It's a common date, currently worth around $2.