Stones

"Tal," I said to two guardsmen who crouched at the side of a fire, playing Stones, a guessing game in which one person must guess whether the number of stones held in the fist of another is odd or even.

"Tal," said one guardsman. The other, attempting to guess the stones, did not even look up.
Outlaw of Gor       Book 2       Page 186

At "Stones," however, I was genuinely pleased with myself. It has two players, who take alternate turns. Each player has the same number of "Stones," usually two to five per player. The "Stones" are usually pebbles or beads, but in the cities one can buy small polished, carved boxes containing ten "stones," the quality of which might vary from polished ovoid stones; with swirling patterns, to gems worth the ransom of a merchant's daughter. The object of the game is simple, to guess the number of stones held in he other's hand or hands. One point is scored for a correct guess, and the game is usually set for predetermined number of paired guesses, usually fifty. Usually your opponent tries to outwit you, by either changing the number of stones held in his hand or, perhaps, keeping it the same. I was quite successful at this game, and I could beat most of the girls. I could even beat Inge, who was of the scribes. I challenged Lana to "Stones," but she would not play with me. Ute, however, of all those I played with, I could not beat.
Captive of Gor       Book 7       Pages 107 - 108

Two others, elsewhere, played Stones, a guessing game.
Marauders of Gor       Book 9       Page 59

"Stones! Guess stones!" called a fellow. "Who will play stones?"

This is a guessing game, in which a certain number of a given number of "stones," usually from two to five, is held in the hand and the opponent is to guess the number. There are many variations of "Stones," but usually one receives one point for a correct guess. If one guesses successfully, one may guess again. If one does not guess successfully, one holds the "stones" and the opponent takes his turn. The game is usually set at a given number of points, usually fifty. Whereas the "stones" are often tiny pebbles, they may be any small object. Sometimes beads are used, sometimes even gems. Intricately carved and painted game boxes containing carefully wrought "stones" are available for the affluent enthusiast. The game, as it is played on Gor, is not an idle pastime. Psychological subtleties, and strategies, are involved. Estates have sometimes changed hands as a result of "stones." Similarly, certain individuals are recognized as champions of the game. In certain cities, tournaments are held.
Magicians of Gor       Book 25       Page 34

The oarsmen were idle, resting, or amusing themselves, some with cards, or the game of stones.
Quarry of Gor       Book 35       Page 85

I gathered that he might have had an unsatisfactory experience at the Golden Chain. If this were the case, I was puzzled. It was not our fault if he was defeated at kaissa or lost a game of stones at the Golden Chain.
Quarry of Gor       Book 35       Page 321