From the article, it seems either the Singapore Army , the US army or the US marines. My bet is on the Marines or the US army because IME if a Singapore soldier did that, the government would mobilize an entire Brigade or more to search for the weapon.
The type of single-use "fire-and-forget" rocket launcher found in a central Queensland town tip and handed into police this morning is used by two overseas defence forces that recently underwent live-fire exercises at a nearby army training area.
The Department of Defence's acting director-general of communications, Colonel Pup Elliott, told smh.com.au the weapon was not Australian Defence Force ordnance.
"I can tell you from the photo straight away it's not one of ours, it's not one of the weapons we use in our inventory."
It is believed the weapon came from the Shoalwater military training area, a short distance from the town of Yeppoon, near Rockhampton, where the tip was located.
Colonel Elliott said the weapon could be traced to an overseas force that recently used the training area.
"We've certainly had soldiers from Singapore, we've had US Marines and [US Army] and I think they all have it in their inventory.
"So we're just going to have ask who had it, and how they accounted for it."
The Matador anti-armour rocket launcher is a 90mm single-use weapon designed by the Singaporean army.
The launcher - already fired and therefore not an immediate threat - was found at a recycling centre attached to a tip at Yeppoon by local man James Maloney.
He told local paper The Morning Bulletin he had paid $2 for it.
"I work in the local theatre restaurant and wanted to use it as a stage prop," he said.
However, when he read a story in a local paper about the army misplacing rocket launchers - based on a story in the Herald - he decided to hand the weapon over.
He gave the weapon to a reporter from The Morning Bulletin who, after contacting the Department of Defence and being told the weapon was not dangerous, kept it for a number of days to photograph it and write a story.
This led to a period of confusion when local police, contacted by Defence, were unable to establish the whereabouts of the weapon.
"The police rang me earlier this evening and they told me they didn't know where it was so I redirected them back to the reporter," Mr Maloney said earlier this week, adding that the last time he saw the weapon was in the back seat of the reporter's car.
The reporter handed it into Yeppoon police station this morning at 8.30am local time (9.30am AEST)...continued