X-Men #11 F+ (6.5)
1st appearance of the Stranger, X-Men cover and story, Stan Lee and Jack Kirby
X-Men #15 F+ (6.5)
X-Men vs. the Sentinels cover and story, origin of the Beast, Stan Lee and Jack Kirby
X-Men #16 VF/NM (9.0)
X-Men vs. the Sentinels cover and story, Stan Lee and Jack Kirby
X-Men #16 VF+ (8.5)
3rd appearance of the Sentinels! X-Men vs. the Sentinels cover and story, likely improvable
X-Men #17 VF+ (8.5)
X-Men cover and story, Stan Lee and Jack Kirby, last Kirby issue
X-Men #18 NM- (9.2)
X-Men vs Magneto cover and story, Stan Lee, very nice book
X-Men #18 VF (8.0)
X-Men vs Magneto cover and story, Stan Lee, nice book with white pages
X-Men #19 VF+ (8.5)
1st appearance of the Mimic!! Stan Lee and Jack Kirby!
X-Men #20 VF/NM (9.0)
X-Men vs. Lucifer cover and story, Stan Lee and Werner Roth
X-Men #22 VF+ (8.5)
X-Men vs Count Nefaria, Plantman, Porcupine, Scarecrow, the Eel, and the Unicorn, Stan Lee story
X-Men #22 VF/NM (9.0)
X-Men vs. Count Nefaria, the Unicorn, the Eel, the Porcupine, the Scarecrow, and Plantman cover and story, Stan Lee
X-Men #23 VF- (7.5)
featuring the convention of lame villains....Plantman, Unicorn, Porcupine, Scarecrow and the Eel
X-Men #23 NM- (9.2)
X-Men vs. the Unicorn, Blizzard, Scarecrow, the Porcupine, and Plantman cover and story, Stan Lee, very nice book
X-Men #25 VF/NM (9.0)
X-Men cover and story, Stan Lee, very nice book of a tough issue