The 1912-S Liberty Nickel has the lowest mintage of the series by far, with only 238,000 produced. The next lowest mintage is the 1885 Liberty Nickel with 1,472,700 produced.
Even though the 1912-S has a very low mintage, the 1885 is more rare. Many 1912-S Liberty Nickels were retained before they had a chance to circulate due to the fact that the coin had a low mintage level and was one of only two issues of the series to carry a mint mark.
As with all issues, striking quality of the 1912-S Liberty Nickel varies, making exceptionally well struck pieces very rare. Many coins of this issue have toned in very attractive gold and lilac colors.
taken from: http://libertynickel.net/