X-Men (Vol 1 1963) Issues 51-100

Due to declining X-Men sales, issues #67 to #93 were re-prints of earlier stories until issue #94 where the new X-Men team were introduced by Chris Claremont and Dave Cockrum, after they starred in Giant Size #1. The new team consists of Colossus (Peter Rasputin), Cyclops (Scott Summers), Storm (Ororo Munroe), Wolverine (Logan), Banshee (Sean Cassidy), Nightcrawler (Kurt Wagner). 

Key Issues; 

#58 - 1st appearance of Havok in costume
#60 - 1st appearance of Sauron
#64 - 1st appearance of Sunfire
#94 - 1st X-Men title appearance of new team. 2nd appearances of Colossus, Storm, Nightcrawler. 3rd appearance of Wolverine
#95 - 3rd appearances of Colossus, Storm, Nightcrawler. 4th appearance of Wolverine. Death of Thunderbird
#100 - Old team vs New team. Beginning of Phoenix origin