I put this set together with my kids in the early 1990's before the card grading services. Except for Card #55, condition varies from card to card of course. Not mint, but there are no major flaws with any of the cards.
In general, the biggest issue with the cards is the centering of the print. I think you will be very pleased with the condition though. Regrettably, the check list card is marked up, but it is the one I have. Even back in the 90's that was a tough card to find.I'm also including the reprint set that came out, but I ran out of space for pictures. The item "1962 TOPPS MARS ATTACKS 55 CARD COMPLETE SET" is in sale since Sunday, February 24, 2019. This item is in the category "Collectibles\Non-Sport Trading Cards\Vintage Non-Sport Cards". The seller is "tomhavel" and is located in Carol Stream, Illinois. This item can be shipped to United States, Canada, United Kingdom, Denmark, Romania, Slovakia, Bulgaria, Czech republic, Finland, Hungary, Latvia, Lithuania, Malta, Estonia, Australia, Greece, Portugal, Cyprus, Slovenia, Japan, China, Sweden, South Korea, Indonesia, Taiwan, Thailand, Belgium, France, Hong Kong, Ireland, Netherlands, Poland, Spain, Italy, Germany, Austria, Bahamas, Israel, New Zealand, Singapore, Switzerland, Norway, Saudi arabia, United arab emirates, Qatar, Kuwait, Bahrain, Croatia, Malaysia, Chile, Colombia, Costa rica, Panama, Trinidad and tobago, Guatemala, Honduras, Jamaica, Uruguay.