according to calgarycoin.com there are four varieties:
Near leaf / with shoulder strap
Far leaf / with shoulder strap
and two "mules"
1953 MULE ERROR 5 CENT
Due to incorrect die pairing a small number of 1951 nickels exist as either "SS far leaf" or "NSS near leaf" varieties, commonly called the SS mule and NSS mule. Some references use SF and NSF as the designations. The NSS (NSF) mules are much rarer than the SS (SF) mules.
Ole