Indian heads

I am not a collector of Indian head nickels (buffalo) and do not know much about them.
Can someone explain or post a link where I can get an understanding of the condition called "2 feathers". A picture of this would be nice so I could see it. Is this condition a one year thing or did this happen many years?
TA
Ms
0
Comments
Lance.
edited to add: here are photos and an explanation
Ms
Successful BST Transactions!SIconbuster, Meltdown, Mission16, slothman2000, RGjohn, braddick, au58lover, allcoinsrule, commemdude, gerard, lablade, PCcoins, greencopper, kaz, tydye, cucamongacoin, mkman123, SeaEaglecoins, Doh!, AnkurJ, Airplanenut, ArizonaJack, JJM,Tee135,LordMarcovan, Swampboy, piecesofme, Ahrensdad,