The first appearance of Major Matt Mason was in this special preview catalog for the 1967 Toy Fair. The entire catalog was re-worked for the Fall Release... the most noticable difference is the missing "Space Rover" from both the front and back covers. This vehicle was removed and the "sky" was lightened for better contrast and more color. The Space Rover went through a couple of design changes before becoming the Astro Trac as we know it.
This catalog also contains several typos and interesting items, such as the "four-color wall poster" offered with all the Crawler sets. I wonder what this poster was supposed to be and why it was taken out before the actual 1967 "Fall" Catalog went to press.