Card fronts advertise a contest where the collector 
has to complete the Bingo card on the back.  The bingo 
is 5x5 with "A" repeated 3 times leaving a total of 
23 different numbers/letters appearing on the fronts. 

The back is the same for all cards.  The fronts also
state the conpleted bingo card must have the 
letters/numbers all from the same series.  

The available cards are all from either the fourth or 
fifth series.  This probably means there are cards from 
the first, second, and third series.