When Gin Rummy became popular in the 1930’s, the scoring of the game was extremely simple. A game consisted of only one column, and was only scored to 100 points. A bonus of 10 points was given for gin or underknocking. There were no doubled hands and when the game was over, if they were playing for money, the winner of the game usually received a very specific amount of money for winning, and a specific amount of money for boxes over that of his opponent. Over the years, in order to add interest to the game, and increase the stakes without actually changing the game stakes as far as the money was concerned, variations were added to the scoring system.
The first and probably most important variation, which to this day has remained a prime function of the game, is what is known as Hollywood Gin, which is not a variation of the game, just a variation of the scoring. In Hollywood Gin, you are playing with three columns. That means that three games are being played at the same time instead of one. The first hand you win or your opponent wins is scored only in the first column. The second hand is scored in the first and second columns, and the third hand and all subsequent hands are scored in all three columns until any or all of these games have ended. If the first column is over before the second, then the subsequent scores are only scored in the unfinished games. The same applies when the two columns are over.
The next important variation that has remained over the years is the bonus boxes. Originally, the bonuses were established as one bonus box for an underknock, two for gin, and three if you have a gin off. Under today’s standardized scoring system, a winning knock receives the difference between the knocker’s count and the count of his opponent’s hand after the opponent receives credit for all the melds and layoffs he has in his hand. On an underknock the score received by the underknocker is the difference between his net count and the knocker’s count plus 25 bonus points. In case you tied, the winner only receives the 25 bonus points. For gin, the winner gets the unmelded count of the losers hand plus 25 points. For both a gin and a gin off, a bonus of two boxes is given to the winner of the hand, while an underknock receives one bonus box.
Another important difference between the old style of play and the more modern one is the fact that anytime that a spade or heart is the suit of the underknock card, the scores are then doubled. That includes the bonus points and boxes. In addition, when either players or teams have each scored in each of the three columns, from that point on all the hands are played with doubled value. That does not mean that if the underknock card was a heart or spade that the score would be quadrupled, because no hand can be more than double value. This is primarily why the final score of the game has been raised, because without it, there would be games that end in just one or two hands.