For his effort, he received an official letter expressing the U.S. Army’s “deep and sincere appreciation.” It hangs in the museum next to photos of the ring.
He also found the bones of many soldiers. Most were identified by forensic experts as Japanese and cremated in the 1990s. About 20 were identified as American, and Mr. Rumaropen said he buried them near his museum. U.S. experts have never examined them.
The Japanese suffered far greater casualties in the Battle of Biak than the Allies. Near Biak, on the tiny island of Musaki, more than 30 skulls and a large pile of human bones believed to be the remains of Japanese soldiers are displayed in a hut.
For some on Biak and smaller islands nearby, acquiring the relics is not about history.
Samggar Usior, a fisherman on Owi Island, a 45-minute boat ride from Biak, began buying relics from scavengers as a young man. He wanted live munitions for gunpowder so he could make bottle bombs to use in reef fishing. Dropping explosives on coral reefs to kill or stun fish has been a common and destructive method of fishing in Indonesia.
When he was in his 20s, a bomb blew up in his right hand and doctors amputated his arm at the elbow. He has been warning people ever since not to make the same mistake.
“It’s all right if you die because of the explosion,” said Mr. Usior, now 60. “But if you’re like me and lose an arm, it’s tough to work in the sea, especially when the wind is strong. Rowing with one arm is like half dying.”
Mr. Wakum said the mortar shells and hand grenades on display in his living room have been disarmed. His collection also includes various kinds of ammunition, gas masks, U.S. and Japanese helmets and hundreds of other items.