Ted, my view is (1) the 150 backs for these three variation cards exist on the original versions of the cards showing their former teams, and (2) some 150-350 subjects -- i.e., these three -- aren't found with 150 backs, just as the cards from the 150-only series aren't found with 350 backs.
It also is worth nothing that G. Brown (Chicago) is part of the 150-only series, unlike Dahlen (Boston) and Elberfeld portrait (N.Y.).
But as I think we've established, a lot of this is just theory. The cards weren't issued with a checklist or a printing schedule. The mystery and the mystique are part of what makes the Monster so much fun to collect, talk about, and even vigorously debate!
Per Dahlen Brooklyn, it looks like you and Pat might have a disagreement on facts. I previously wasn't aware of either (1) what Pat said above in post #24, or (2) what you said above in post #31 regarding the notation being found on cards across the five series. I'm not in a position yet to draw a conclusion on this question.