I don't know about the Avalon, but a guess is that the 12 1/2 cent chips were used for Pan kondition value @ half the rate of a 25c Pan game. Blackjack wasn't legal in California at that time.
The San Souci 12 1/2 cent chip from Las Vegas likely was for BJ payoffs on a 25c minimum game.
There's also a 12 1/2 cent chip from Club Bingo, downtown Las Vegas. Used on a 25c BJ game as well.
As for the 70 cent Keno chip from Union Plaza, that was the cost of a single Keno game at the time it was in use.