Ron Guth:
With an ample mintage of almost 12 million coins, the 1912-D Dime is common and readily available in most grades. In Mint State, the 1912-D Dime is most common in the grades of MS63 and MS64, though MS62's and MS65's are also well-represented. Finding MS66 examples can be challenging, but they are great values. MS67's are very rare. Only one PCGS MS67 1912-D Dime has appeared in recent decades, but it has appeared in three separate auctions, giving the impression that it is more common than it really is.
In general, 1912-D Dimes are well struck and often come with excellent eye appeal.