I recently posted my 1959 Bazooka set on imageevent.com. It took me almost 20 years to complete, with the Groza being the last card to finish the set. I had to borrow 600.00 from my Dad in the 1996 to purchase it as I had just returned from the National Sports Collector's Convention in fruitless pursuit of finishing the set (but spending my last dollar anyway), and a letter arrived from Don Niemi telling me he had one! According to Don, he felt the Groza was the toughest in the set and that there were less than 15 or so in existence (don't know how he came by those numbers). He also said he felt it was one of the 5 rarest football cards in the hobby.
http://imageevent.com/supplex55/1959bazookafootballset