X-Men #44 F+ (6.5)
1st Silver Age appearance of Red Raven, X-Men cover and story
X-Men #45 VF+ (8.5)
Cyclops vs. Quicksilver cover, X-Men cover and story
X-Men #45 VF- (7.5)
X-men cover and story, looks way better but has a small slice at top left (visible)
X-Men #49 CGC 5.0
1st appearance of Polaris, X-men cover and story, Stan Lee, cover and art by Jim Steranko!
X-Men #50 CGC 9.2
1st Polaris cover appearance, Polaris & Magneto vs. the X-Men cover and story, Stan Lee and Jim Steranko
X-Men #51 NM- (9.2)
X-men cover and story, Stan Lee, cover and art by Jim Steranko!
X-Men #51 CGC 9.0
1st appearance of Eric the Red, Jim Steranko cover, X-men cover and story and art by Jim Steranko! Magneto and Polaris appear, origin of the Beast
X-Men #51 VF+ (8.5)
X-men cover and story by Stan Lee, cover and art by Jim Steranko!
X-Men #52 VF (8.0)
X-Men cover and story, Magneto, Polaris, and Mesmero appear
X-Men #53 VF (8.0)
X-men vs. Blastaar cover and story, Stan Lee story and cover and art by Barry Windsor Smith, his first comic book work
X-Men #56 F/VF (7.0)
Neal Adams art begins, X-Men cover and story, 1st appearance of Havok without costume
X-Men #56 CGC 9.2
1st appearance of the Living Monolith! X-Men vs. the Monolith cover and story with Neal Adams cover and art!
X-Men #58 CGC 8.5
1st Havok! X-Men cover and story by Roy Thomas with Neal Adams cover and art!
X-Men #58 F+ (6.5)
1st Havok! Neal Adams cover and art! X-Men cover and story by Roy Thomas and Neal Adams
X-Men #60 F/VF (7.0)
Neal Adams cover and art, 1st appearance of Sauron! X-Men cover and story
X-Men #61 CGC 9.2
X-Men vs. Sauron cover and story, Neal Adams cover and art! 2nd appearance of Sauron
X-Men #61 VF+ (8.5)
X-Men vs. Sauron cover and story, Neal Adams cover and art!