Posted By:
FatBoyMorning Mike,
I'm assuming you mean by "I only have examples of the No Ad back among the first fifty, and none from among the second series" you're talking about the omitted address at the bottom on the backs of the cards?
I do have 2 boxers that have this variation including #76 Johnson, but none in the second series. So....yes, I've always thought the same, no omitted address backs in the higher series cards (#77-126)...nor do I ever remember seeing one. Craig is better suited to answer this, but I think if I did ever see one, it would stand out to me.
My Johnson has the advertising back too BTW. As for certain cards having only one back style...never thought about that one too much, we'd have to compare notes 
. Again...Craig is the man for back related questions.
K