The 1905-S Half Dollar is a surprisingly scarce date. The overall population of certified examples is larger than the 1905 and slightly larger than the 1905-O, but the number of certified Mint State examples of the 1905-S is far smaller than either the 1905 or the 1905-O. In reality, the 1905-S tracks the much more popular 1904-S in most Mint State grades, yet the 1905-S sells for much less.
The top end of the condition scale includes several MS67 1905-S Half Dollars, all but one of which have crazy, colorful toning. The one exception is the former Price-Duckor PCGS MS67 which displays delicate, golden peripheral toning around frosty white centers. Most 1905-S Half Dollars are struck well.