Answer:.All authentic 1912-S Liberty nickels were struck from a die that displays a bulge in the left field, approximately extending from star 5 through star 8. In addition, all authentic pieces have weakness at the very highest details of the hair, in the general area beneath the word LIBERTY.
If any variations exist, such as a sharply struck piece from a die not showing a bulge, I have not seen one. I presume that all of the 238,000 struck (a small mintage) are the same.