It come from the 1968 Atlantic Oil Play Ball set. A total of 50 cards were in the set, 40 regular cards and ten that won you some cash.
You'd get the game piece after buying some gas, and then open it up to see which player you got. There were five winners from each league, two worth $5, two worth $10, and one would get you $100.
The Santo card was a loser, but he was the only Cub loser in the set.
Ernie Banks has a card and it you got it, you won $100. Go Mr. Cub!
Billy Williams has a card and it is a $5 winner. Nice job, Billy!
Needless to say, the Billy and Ernie cards are extremely scarce. After all, why would some one not redeem the card for some cash.
Both Billy and Ernie's cards from this set are not included on PSA's master set. I'm guessing that no collector has got one to submit to be included on the list. I couldn't even find an image of one. Nothing on Google Images, ebay, PSA, or any of the other usual places.
I can safely say that this is one Cub set that I will never, ever complete.
But thank you Mark for one of the three!