New analysis shows an old cannon found on a Northern Territory beach in 2010 by a schoolboy may have originated in Spain, further bolstering the case for it being among Australia's earliest evidence of European contact.

The cannon, known as a swivel gun, was found by schoolboy Chris Doukas at Dundee Beach.

Analysis of sand inside it showed it dated to the 1750s, plus or minus 40 years.

Because it looked like a Portuguese swivel gun from the 1500s some had thought it could have re-written the history of Australia, by showing Portuguese set foot on Australian soil well before Captain Cook reported seeing Australia's eastern coastline in 1770.

Claims the swivel gun was Portuguese were discounted by curator at the Museum and Art Gallery of the Northern Territory, Paul Clark, who said it was likely to be a copy of a Portuguese or Dutch swivel gun, and lost overboard by Macassan traders.

But Dr Matthew Cupper from the University of Melbourne, who performed tests on the lead the cannon is made from, said comparing it to many hundreds of different mines around the world showed it most closely resembled lead found at the Coto Laizquez mine in Andalusia, a region of Spain.

"That doesn't mean it definitely comes from Andalusia, just that its isotope signature most closely matches the Andalusian samples," Dr Cupper told the ABC.

"The lead may also have been recycled, with lead tiles from Europe taken to Indonesia and melted down to make something else."

He said the lead's isotope's signature was also somewhat similar to another lead mine on the Mediterranean island of Sardinia.

The Past Masters heritage group, which has been driving analysis of the swivel gun, said the latest information was proof the artefact was not Asian in origin.

"This truly is the 'smoking gun' of the Portuguese discovery of northern Australia", the group said on their Facebook page.

Mr Clark said the latest evidence was a new piece in the puzzle of the swivel gun but claims it was a smoking gun to prove it was not Asian were "overblown".

"That is a very long bow to draw," he said.

Mr Clark said analysis of the tin content in the cannon could prove more conclusive.

The first documented encounter with Australia by a European vessel was by Dutchman Willem Janszoon in 1606.