The "Big Maple Leaf" coin, which bears a portrait of Queen Elizabeth II, has a market value of $4.5 million.
In a brazen heist, suspects used a wheelbarrow to steal a 100-kilogramme (221-pound) gold coin worth millions from a museum in Berlin.
The coin known as the "Big Maple Leaf" was stolen from Bode Museum on Monday, leaving investigators perplexed over how such a heavy item could be taken so easily.
Berlin police has now come up with an explanation.
At least two burglars broke into the museum using a ladder to climb up to a window from elevated railway tracks running alongside the building.
The thieves grabbed the coin, on loan to the museum's coin collection, loaded it onto the wheelbarrow, then carted it out of the building and along the tracks across the Spree river before descending into a park on a rope and fleeing in a getaway car.
Police say the three-centimetres (1.2-inch) thick coin, with a diameter of 53 centimetres (20.9 inches) and valued at $4.5 million for the gold alone, was likely damaged in the theft.
According to German media, the stolen coin is a commemorative piece issued by the Royal Canadian Mint in 2007.
It features the portrait of Queen Elizabeth II.
Suburban rail traffic was interrupted as investigators combed the area for clues.
The Bode Museum, located on the German capital's UNESCO-listed Museum Island, houses one of the world's biggest coin collections.
The holding includes 102,000 coins from ancient Greece and about 50,000 Roman coins.