X-Men #40 CGC 9.8
Highest Certified1st appearance of the Frankenstein monster at Marvel, X-men cover and story by Roy Thomas, Don Heck, Werner Roth and George Tuska
X-Men #42 VF+ (8.5)
Death of Professor X, X-men cover and story by Roy Thomas and Don Heck
X-Men #44 VF- (7.5)
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+ (8.5)
Cyclops vs. Quicksilver cover, X-Men cover and story
X-Men #45 VF/NM (9.0)
Cyclops vs. Quicksilver cover, X-Men cover and story
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 9.4 SS
Classic Steranko cover, 1st Polaris cover appearance, Polaris & Magneto vs. the X-Men cover and story, Stan Lee and Jim Steranko, signed 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 #52 VF- (7.5)
X-Men cover and story, Magneto, Polaris, and Mesmero appear