The $20 chips were used in Baccarat so the dealers could quickly calculate the 5% commission on banker bets, $1 per $20 wagered.

When the mini baccarat tables came out with $5 minimums, a 25 cent commission per $5 wagered made the $20 chips obsolete. $25 chips were used to "force" bigger bets.

Today's mini bac tables eliminate the 5% commission and instead have a 3-card 7 banker winner as a push for the banker and loser for the player.