Yeah, I'm calling bullshit on his story. He probably had an ancestor who fought in the Pacific. Trophy taking was a common practice (NSFW description below):
https://en.wikipedia.org/wiki/American_mutilation_of_Japanese_war_deadQuote:
Eugene Sledge relates a few instances of fellow Marines extracting gold teeth from the Japanese, including one from an enemy soldier who was still alive:
But the Japanese wasn't dead. He had been wounded severely in the back and couldn't move his arms; otherwise he would have resisted to his last breath. The Japanese's mouth glowed with huge gold-crowned teeth, and his captor wanted them. He put the point of his kabar [combat knife] on the base of a tooth and hit the handle with the palm of his hand. Because the Japanese was kicking his feet and thrashing about, the knife point glanced off the tooth and sank deeply into the victim's mouth. The Marine cursed him and with a slash cut his cheeks open to each ear. He put his foot on the sufferer's lower jaw and tried again. Blood poured out of the soldier's mouth. He made a gurgling noise and thrashed wildly. I shouted, “Put the man out of his misery.” All I got for an answer was a cussing out. Another Marine ran up, put a bullet in the enemy soldier's brain, and ended his agony. The scavenger grumbled and continued extracting his prizes undisturbed.