You are purchasing a lot (500 coins) of Buffalo Nickels all "NO DATE" COINS.  These coins have "not" been acid dated.  I have checked for acid treated and have not found any, but it could be possible for one or two to slip through in a group this large.

THEY ARE AUTHENTIC BUFFALO NICKELS THAT ARE A NOVELTY, PERHAPS USED AS JEWELRY.  OR YOU COULD ACID DATE THEM IF YOU ARE INTO THAT.