It was a small oval-shaped “fruit” with a slightly pointed end and covered with a dark-brown velvety shell. The inside was a golden brown pulp that was rather sour, but tasty. Plentiful during my primary school days, when it was sold in newspaper cones at the school tuckshop. I believe it is called Buah Keranji.
But the main event was slugging it out. One would choose a “champion” buah, and then challenge an opponent with his “champion”. The two buahs were butted against each other until one of them cracked open. The loser would then be taken by the winner.
In the event that the opponent lost three times in a row, he had to give his whole packet of buah to the winner. Those were the days of fun.