Advancing Odds / Scores
The first couple of bingo machines were fixed payout. You always got the same number of credits for 3, 4, or 5-in-line wins.
Advancing odds changed that. You can maybe increase the number of credits you can win by depositing more coins/credits before shooting the first ball (and sometimes after the first ball, on games with the stop and shop score booster feature).
A typical 3-in-line payout on an early machine with ten odds steps would be: 2 4 6 8 12 16 24 32 48 64
The first coin inserted would reset the machine to the 2 level, successive coins would increase it zero or more steps. Zero is the main reason the machines are considered gambling devices in many areas. You can deposit a coin and the odds may not increase (at least they never get worse, like on some early one-ball machines).
In the late 70's in a effort to distance the games from legal definitions of gambling devices, the advancing odds feature disappeared again on some machines. In addition, there were a few games made between 1956 and the late 70's that didn't have this feature either. These games were usually for territories where standard bingos were illegal.
BINGOS - FOR AMUSEMENT ONLY