From the artist:
Cornerboxes were a Marvel Comics Phenomenon during what are known as the Silver and Bronze age of comics, roughly the early 60's to mid 80's. The upper left corner of the cover was reserved for the issue price and numbering along with a classic graphic of the character(s). They're such a cool reminder of how explosive and awesome that era of Marvel comics was. A rebuilt graphic from a cover scan, I've endeavored to keep as much of the original graphic as possible.