It was winter of 75-76 (because it was snowing in Flagstaff), and my family took a trip from LA to southern Arizona up to the Grand Canyon.
At the Grand Canyon lodge / store / something of that sort, my mom offered to buy me a comic book from the spinner rack. I was no dummy. I had some back issue X-Men (including a faboo Neil Adams issue #59 [http://marvel.wikia.com/wiki/X-Men_Vol_1_59]), plus this was a Giant-Size X-Men.
My mom forked over the 50 cents. I read the darned thing eleventy-dozen times. (My mom read it through at least once as well; I remember her reading aloud a line from Banshee — "Faith and begorrah, it's Professor X").
My copy is probably "Good" quality at best, but it's bagged and boarded.
Good times, and an inadvertent issue of a milestone (and iconic covered) comic book.
Giant-Size X-Men 1, '75. Features the first appearance of my favorite team of superheroes, Colossus, Nightcrawler, Storm and Thunderbird. #xmen