1909-S 10C MS67 Certification #06666260, PCGS #4853
The 1909-S Dime is the most valuable of the 1909 Dimes by just a small margin (over the 1909-D). The largest certified population is in MS64. Above that, the number of MS65's drops off dramatically, MS66's are equally rare, and MS67's are fewer than the number of fingers on one hand.
The strike quality of the 1909-S Dime can be slightly mushy, so keep an eye open for fully struck examples (paying particular attention to the leaf structure on the lower reverse). Positive eye appeal is always appreciated and there are some lovely, high-end coins with great color. The PCGS MS67 illustrated above (formerly in Bob Simpson's collection) is particularly attractive.