Iron Man #55 is the definition of a Bronze Age MEGA KEY.  It contains the first appearances of Thanos, Mentor, Drax the Destroyer, Starfox, Kronos, and the blood brothers.  Almost anyone would put this in the list of top 10 Bronze Age books.  It is still affordable, and we believe, undervalued.  This book is graded 9.4 NM with white pages by CGC.  It has nice alignment, color and gloss.  Get your copy before it is over $20k!