X-Men #37 VF/NM (9.0)
X-Men cover and story, very sharp, a bit of tanning along the edges
X-Men #38 F+ (6.5)
X-Men vs. the Blob and the Vanisher, origins of the X-Men back up features begin
X-Men #38 VF+ (8.5)
X-men cover and story, Very pretty copy, very white cover
X-Men #40 CGC 8.5
1st appearance of the Frankenstein monster at Marvel, X-men cover and story
X-Men #42 VF- (7.5)
Death of Professor X, X-men cover and story by Roy Thomas and Don Heck
X-Men #43 CGC 9.4
X-Men vs. Magneto cover and story, Scarlet Witch and Quicksilver appear
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