The "Three-Move Opening" system was first introduced into national tournaments in the USA during 1934 in an attempt to improve on the number of wins being scored in major events. Many of the players at that time considered the GAYP style of play as being obsolete, while the "Two-Move" system (then in use) produced too many drawn games. Although not being accepted into Britain until the 1950's, the three-move opening system is now the method of choice in determining national championships in most countries.
A "Three Move Opening" is the making of a random selection of three moves (two for Red and one for White) to commence a game, after which players have complete freedom to continue from the opening sequence chosen. The selection of an "opening" is determined by the drawing of cards from a pack of "Three Move Opening Cards". This is a special pack of cards that have all of the current three-move openings in use printed on them. (See example below)
The "Deck" is made up of a pack of cards with six - eight three-move openings printed on each. At the commencement of play the cards are shuffled by the tournament or match referee and one of the players draws a card out. Each of the cards also has a letter (A-F) printed on them, which correspond with the letters printed immediately before each opening. After the first card is drawn, the letter printed on it is noted (e.g. "D" as above). The card is then replaced into the pack and the second player draws another card. The letter printed on the first card will determine the opening to be played on the second card - i.e. the opening after the letter (d).
In total there are 302 ways in which the first three moves (R-W-R) can be made. If we leave aside the 83 duplicates (e.g. 9-13 24-20 10-14 = 10-14 24-20 9-13) and the 45 that result in the loss of a man (e.g. 10-14 21-17 14x21), we are left with 174 playable 3-move ballots. Of these, 18 were now considered unsound (untenable), leaving the remaining 156 in current use.