This is the holy grail of the Marvel Age series, for sure!  Besides having an awesome cover of Marvel's heroes by Michael Zeck, this book features the first look at the black costume that debuted 2 months later in Amazing Spider-Man #252.  The story behind this is quite interesting.  Marvel Editor-in Chief Jim Shooter paid a Marvel Comics fan named Randy Schueller $220 for the ownership of the rights to the costume concept.  That prototype, or design preview of the iconic costume is contained in Marvel Age #12.  The rest was history.  This book is graded 9.8 NM/MT with white pages by CGC.  It's a perfect copy, with great alignment and color.  Oh, and only 166 CGC 9.8's exist as of this listing!