Picture: Koorana Crocodile Farm/Facebook

Canberra - The owner of a crocodile farm in eastern Australia was baffled to find an orthopaedic metal plate and screws in the stomach of a dead 4.7-metre saltwater croc, he told dpa Wednesday.

MJ died in June at Koorana Crocodile Farm in Coowonga, near the Great Barrier Reef, in Queensland, six months after an all-night fight with a crocodile of the same size.

Farm owner John Lever told dpa that the crocodile had stopped eating altogether before dying, adding he was shocked to find the stainless steel plate complete with six screws in MJ's stomach upon examination.

"There was no bone. It must have been eaten away by the crocodile's stomach juices. Also, there is no identification number. The surface of the steel had been corroded by the stomach's acidity," he said.

Lever said he has been told it is an old-style, Swiss-made orthopaedic plate with modified screw holes that are oval instead of round.

"It could have been there for decades. We think it could belong to a person... We have been told now this is a human orthopaedic plate," Lever said, adding he posted an appeal for information on social media. 

Lever, who had bought the crocodile over six years ago from another farm, said police have not yet been involved. 

Each year, some 30,000 tourists visit the farm, which has 5,000 crocodiles. They also harvest the reptile for skin, leather and other products, which they sell to Europe, and serve its meat in their restaurant.