Question about series

[Lueth2048]

I started collecting baseball cards at the age of eight in 1972. in 1972 and 1973 I had no idea about how cards were released in series. I know the final series in 1972 reached our neighborhood when it was still warm out (I remember the kid across the street showing me the Jose Cardenal Traded) and in 1973 my memory is that the series releases were different than they had apparently been in the past. I never became sophisticated about how series releases were handled. I remember the boxes in 1972 saying things like 4th Series, but this didn't mean anything to me.

Does anyone here remember the approximate release dates for each series? Were they radically different when there were seven series issued? Were the 1950s and 1960s similar or very different?