I love the Kellogg 3D cards and boxes. I collected them during the entire run.
I think the hobby is wrong on some of the mail-in information that has circulated for years. I think 1973 was the first year for the mail-in offer. I challenge anyone to show a box from 1970 or 1972 with a mail-in offer. For 1970 and 1972, I think the only reason they are more common than 1971 is that card dealers were able to get supplies of those two sets from Kelloggs and were not able to get them for 1971.
Also, if my memory is correct, I think in 1981 and 1982 you could only mail in for complete sets, I don't think the cards were in boxes those years. They were back in boxes for the last year of 1983.
