A group of Berlin thieves pulled off an improbable heist early Monday morning, breaking into a German museum with a ladder and carting away a 100-kilogram gold coin named the "Big Maple Leaf" in a wheelbarrow.

Between 3:20 and 3:45 on Monday morning, thieves entered the Bode Museum through a window and stole the coin, which was originally issued by the Royal Canadian Mint. It has a face value of $1-million but, according to current gold prices, could be worth at least $5-million.

Martin Halweg, a spokesman with the German police, told The Globe and Mail that the suspects are believed to have set up a three-metre-long ladder, which enabled them to enter at the back of the Bode next to a set of railway tracks. They then used a wheelbarrow to remove the valuable, which is one in a series of six certified by Guinness World Records because of its size and 999.99/1000 gold purity.

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Pictures taken before the burglary show that the coin, which is three centimetres thick and roughly as wide as a car tire, was displayed inside a glass-enclosed, bulletproof cabinet. Like all Canadian gold coins, it bears the portrait of Queen Elizabeth II on the obverse side.

The coin has been on display since 2010 and was part of the Munzkabinett collection, Berlin's most important archive of coinage, which includes more than 540,000 objects.

No other thefts have been announced.

A Berlin police communiqué said a museum security staffer alerted police after 4 a.m.

Quoting unnamed police sources, the German newspaper Bild said that the thieves took advantage of construction work at the museum and that the chances of its recovery are slim because the coin could be promptly melted.

Police later had to interrupt service on the S-Bahn rapid-transit system after they discovered the ladder on rail tracks near the Bode, which is at the tip of an island on the Spree River, in the middle of the German capital.

It is not clear how this seemingly old-hat operation eluded the museum's high-tech alarm system.

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The police communiqué asked the public to report any occurrence where someone had offered to sell large, unusual volumes of gold.

The big coin exhibited by the Berlin museum was on loan from an owner who had purchased it from the Royal Canadian Mint.

The mint had made six of them in 2007 to promote a new line of high-purity bullion.

A Royal Canadian Mint spokesman said five of the giant coins were sold while the sixth remains in a vault in Ottawa.

When asked what the thieves could do with the coin, police spokesman Winfred Wenzel told the German newspaper Die Welt: "Either they were hired to do it by someone who wanted to have the coin, but it's more likely that it will be melted down."