The Mystery Coins of Marchinbar

In 1944, a soldier on a remote Australian island found a handful of copper coins. He dropped them in a tin and forgot about them. When experts learned of the find 33 years later, they traced some of the coins to medieval Africa – very much out of place and out of time. It’s a great mystery, not least because the answer is settled enough to scratch the ‘I-gotta-know-what-happened’ itch, but not so much as to preclude the fantastic. And it’s a great plot hook. Let’s take a look!

The Wessels are a 75-mile-long island chain off the coast of northern Australia. Marchinbar Island is the largest among them. The Wessels sound a lot like paradise: sandy beaches, rocky cliffs, plateaus, forests, grasslands, and mangroves. Because of prevailing winds, for several months a year, anything blown off course in the Arafura Sea winds up in the Wessels. And stories persist among the indigenous Yolngu people of a hidden cave in the Wessels filled with treasure and antique weapons…

Marchinbar Island is circled, off the northeastern tip of the Northern Territory

During WWII, Australia maintained a lookout post on Marchinbar Island. In 1944, one of the soldiers there dug up nine coins along the seashore. He put them in his bag and forgot all about them until 1979, when he tried to have them identified. Four were from the Dutch East India Company, all dating 1690-1784. The other five were from the Tanzanian Sultanate of Kilwa, a small state founded on the African coast by a Persian prince. Finding Kilwa coins in Australia was remarkable. Other than the Marchinbar coins, only one Kilwa coin has been found outside Tanzania: in Oman, 5,000 nautical miles from Marchinbar. The Kilwa coins are hard to date, but the oldest bear the following text: “Sulaiman ibn al-Hasan trusts in God, the Master of Favours.” Sultan Sulaiman ibn al-Hasan of Kilwa was minting coins in the years 1294-1308. That’s centuries before anyone outside Australia knew the continent was even there.

Reconstructing how the coins got to Marchinbar has proven difficult. Since the Dutch and Kilwa coins were found together, they were probably deposited at the same time, in a single batch. That’s not implausible. This was still the era when the value of a coin was based principally on its metal content. A Kilwa coin would still have held value in 1784 (when the last Dutch Marchinbar coin was minted), even though Portugal conquered Kilwa in 1505. And pre-conquest Kilwa was part of a trading network that connected East Africa and the South Pacific. So Kilwa coins and Dutch coins could have been found together in circulation in the South Pacific in 1784.

But how did they get to Marchinbar Island? The answer may lie in the island’s aboriginal people, the Yolngu. The late 1700s to mid 1800s (when the coins were probably deposited) was a bad time for the Yolngu. Smallpox was raging in the population, and the survivors resettled elsewhere, leaving Marchinbar completely depopulated. Before they were forced to leave, the Yolngu had spent a century trading with Indonesian fishing fleets which passed by the Wessels on expeditions to fish for sea cucumbers.

Given all this, we have a few possibilities:

1. An Indonesian fisherman could have dropped the coins on the beach when stopped at Marchinbar for water.

2. A Dutch, Portugese, or Arabian shipwreck could have been carrying both Dutch and Kilwa coins, even if only in the pockets of the sailors, and thrown them up on the beach after a storm.

3. The Yolngnu could have acquired the coins in trade with the Indonesian fishing fleets. Dr. Ian McIntosh of Indiana-Purdue points in particular to a fisherman named Buthimang. Buthimang was shipwrecked in the Wessels, adopted into a Yolngu clan, and lived with them as a nearly full member of the clan until he was murdered as an old man in the mid-1800s. The Yolngu did not use currency at the time, and may have given Buthimang all the coins they acquired in trade, figuring he was the best repository for items of apparent ritual significance to his former people.

A 1572 European depiction of Kilwa

One of the above explanations is probably true. But it doesn’t have to be so at your table! It’s child’s play to connect the Marchinbar coins to the story I teased at the beginning about Yolngu tales of a secret cave filled with treasure and antique weapons. At your table, you can set a Marchinbar-style adventure on any remote island previously or currently inhabited by an indigenous culture, then later home to an army outpost.

If we’re building a fictional story, let’s assume that the Yolngu (or your campaign’s equivalent) maintained a cave where they kept all the treasure they salvaged from shipwrecks. Centuries of storms brought them Arab treasure, Portugese treasure, Dutch treasure, Indonesian treasure, and yes, Kilwa treasure. By the time the Yolngu abandoned Marchinbar, the cave was piled high with cannons, swivel guns, chandeliers, and piles and piles of coins, separated not by country of origin but by color: tarnished black silver, flaky green copper, and shining gold.

One day in the 1940s, when the cave had been forgotten for generations, an animal got inside. Moving blindly in the darkness, it bumped into a pile of green coins. Nine rolled out of the cave mouth: four from the Dutch East India Company, and five from Kilwa. A flash flood carried them to the beach to be discovered by a soldier at a remote lookout post: the grandfather of one of the PCs.

In the present day, the PCs get a message: the grandfather has passed away and left his grandchild these nine coins and a map to where he found them. Should the PCs identify them, they’ll learn the Kilwa coins are very valuable. At this point, the PCs should pick up some rivals: folks who hear of the discovery and think there may be a larger treasure. These rivals might be an unethical band of treasure hunters. Or they might be white supremacists, concerned about Australian history being ‘polluted’ with an African connection. Assholes like that are always fun antagonists. The rivals will take a peek at the map, and may even steal it outright, if the PCs aren’t careful.

When the PCs are traveling to the island, their rivals will attack! It’s an opportunity for a fight on a boat or a plane, and I have literally never not enjoyed one of those. Once the PCs reach the island, finding the site on the map may be tricky. An expedition in 2014 had a great deal of trouble finding the site based on the real-world map, because seventy years of storms had changed the coastline so much, it no longer resembled the map. Having the party tromping all over the island also gives the party’s rivals another chance to strike! When the PCs find the spot where granddad picked up the coins, they can trace the landscape ‘upstream’ to learn where the coins came from, and thereby find the cave!

Once they find the treasure, if the PCs are good guys, they’ll tell the modern Yolngu (or your campaign’s equivalent) about it. If both sides act in good faith, they should be able to find a way to split the treasure so the PCs are rewarded for their work and the Yolngu-analogues regain a piece of their cultural heritage thought lost. Of course, these negotiations represent the last opportunity for the party’s rivals to strike! If your campaign includes supernatural elements, you could even introduce the ghost of Buthimang as the caretaker of the treasure: an outsider who volunteered to guard these outside artifacts until he was no longer needed.



Life and Death on the Wessel Islands: The Case of Australia’s Mysterious African Coin Cache, by Professor Ian S. McIntosh, Australian Folklore 27, 2012

The Museum of Applied Arts and Sciences

Australian Geographic

The Indian Ocean and Swahili Coast coins, international networks and local developments by John Perkins


Everyone needs content for their RPG campaigns: adventure hooks, puzzles, NPCs, political machinations, combat encounters, and adventure sites. That’s what this site provides! I draw RPG content from real-life fact and folklore, then give advice on how to adapt it to your fictional campaign. I believe content that is grounded in reality (however fantastical) is richer and more vibrant, and your players will appreciate the difference.


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