The Baseball Diamond is a valuable jewel which, along with the trophy it stands on, is awarded to the winning team of an international baseball championship.
The diamond is fairly large and sits on a gold trophy of a baseball player holding up a bat. It is kept in a glass container.
The Baseball Diamond stayed with whatever team won the championship, which had always been Japan. However, during one championship, the American team was on the verge of defeating the Japanese team and taking the trophy home with them. This proved problematic for Mr. Husai, who had stolen the diamond and replaced it with a fake. He was worried that if the Americans took the trophy home, they would discover the fake diamond. To prevent this, Mr. Husai halted the games by disguising himself as the Dragon Beast and scaring everyone away from the stadium. Velma Dinkley figured this out and, to confirm her suspicions, purposely fumbled the trophy so that the diamond would collide with the glass casing. The glass didn't crack, proving the diamond was fake.