The 1917-S Lincoln cent is one of the semi key dates in the wheat Lincoln Cent series. As it is, most San Francisco struck cents from the teens and twenties are very difficult to find in uncirculated grades and many times even in circulated grades.
In circulated grades the 1917-S becomes a bit difficult to find in XF condition and higher. In uncirculated grades most examples range from MS60-64 with possibly just under 1,000 examples surviving in these grade ranges. It will require a lot of searching and several hundred dollars to acquire an example in MS60-MS64condition. Examples in MS65 condition are considered elusive as there are probably about 50 examples in this grade only, with very few being finer. In MS66 condition it is considered very scarce as of 2011 PCGS has only graded one lone example in MS66 condition.