While regular 1942 Mercury dimes (especially from Philadelphia, Denver, and San Francisco) are common and worth a few dollars, certain varieties are extremely rare and valuable.
The most famous and valuable 1942 Mercury Dime is the 1942/41 overdate error, where a 1942 date was struck over a 1941 die. It is easily visible to the naked eye with magnification and drives huge collector interest.
The overdate happened at both the Philadelphia (no mintmark) and Denver (D mintmark) mints. The Philadelphia version is rarer and more valuable than the Denver variety.
An incredible 1942/41 Mercury Dime graded MS67 FB (Full Bands) by PCGS sold for $120,000 at auction — thanks to its superb condition and clear overdate.
Coins designated "Full Bands" (showing complete separation on the fasces bands) are extremely desirable. A non-FB example might be worth thousands — but an FB one can be worth tens of thousands more.
Regular 1942 Mercury Dimes (without the overdate) are worth around $2–$5 in average condition but can reach $100+ in pristine Mint State grades, especially with Full Bands.
Due to high value, many counterfeits or misidentified coins exist. Serious collectors insist on certification from top grading services like PCGS or NGC to ensure authenticity.