Several years before the June 2007 Sotheby's auction, Mastro Fine Sports offered the same complete set in their 4-22-2003 auction. Attracting 19 bids, it sold for $13,915, a price I believed to be "a steal". This sale was mentioned in my book, NEVER CHEAPER BY THE DOZEN, in the chapter I devoted to the 1960 Post Cereal. I was unaware of Sotheby's offering the set in 2007; naturally, I would have included that offering, particularly since it nearly doubled in price from the Mastro sale, being won at $27,000.
My prized the 1960 Post Cereal Mickey Mantle also is unstained on its backside.
I thought I remember Post putting a strip of glue on the wax bag holding the cereal to keep it in place whilst the assembly moved toward the mechanism that dumped the Grapes Nuts Flakes into the bag. It would seem the glue would have been placed on the bag facing the backside of the box front.
I wasn't at the plant, of course, being just 6 years old at the time of the '60 Post. Trying to figure this matter out is fun, nonetheless.
Some people gave me some fascinating anecdotes and insights for that chapter---hint, hint.
---Brian Powell
PS--Austin Mike---PM about your 1960 Post Cereal Mantle; I want to discuss it with you.