The nighttime theft, which took place in March 2017, saw the disappearance of a coin once recognised as one of the largest in the world.
The coin is valued at €3.75m.
A ladder, a wheelbarrow and a getaway auto were allegedly used in the heist.
Investigators believe the suspects cut up the coin and sold the pieces.
A defence lawyer told the court that police had presented "not a single shred of evidence" to show that the Remmo men had stolen the coin.
Also in the dock in the juvenile trial is a former museum security guard, 20-year-old Dennis W., who allegedly acted as the inside man, giving the others crucial information for the break-in.
Prosecutors assume the almost pure-gold treasure, which has a face value of one million Canadian dollars, was either cut up, molten down or taken overseas.
Struck by the Royal Canadian Mint in 2007, the Big Maple Leaf coin was feted by the Guinness Book of World Records as the world's largest coin.
The coin, which was on loan from a private collection, was stolen from the Bode Museum in March 2017 in Berlin.
Security camera footage from the night shows three young men wearing dark hoodies, scarves and baseball caps make their way to the museum.
Prosecutors say three of the suspects broke into the museum through an upstairs window and used a ladder, wheelbarrow and rope to extract the coin from a bullet-proof glass. They apparently dropped the coin twice on the floor during the heist.
The auto that police say is the getaway vehicle was later confiscated during an illegal auto race, reported Spiegel Online.
However, a police team discovered gold particles inside the vehicle matching the purity of the Big Maple Leaf, according to prosecutors.
The fourth suspect, a schoolfriend of one of the defendants who was a guard at...
Police a year ago targeted the Remmos with the seizure of 77 properties worth a total of €9.3m, charging that they were purchased with the proceeds of various crimes, including a 2014 bank robbery.