But its humble appearance belies its significance and only its almost symmetrical shape offers up a clue to its true origins.

In April 1770 it was a shield belonging to the traditional owners of Botany Bay, the Gweagal people, collected when Captain James Cook first landed on their shores.

And for the first time since it was taken almost 250 years ago it's about to return to Australia.

The shield is one of the star items in the National Museum of Australia's latest exhibition Encounters, bringing together 151 Aboriginal and Torres Strait Islander objects held by the British Museum.

Along with the masks, shields, spears, didgeridoos, baskets and head dresses, collected between 1770 and the 1930s, are 138 contemporary items – many specially commissioned for the landmark exhibition.

Most of the British objects haven't been seen in Australia since they were first collected, including two spears also taken during the Cook encounter, and now held by the University of Cambridge.

To say it will be an emotional experience when the items return to Australian shores is an understatement for the chairman of the museum's Indigenous Reference Group, Peter Yu.

"Imagine the encounter on the beach that day when Cook landed … this kind of awkward dialogue between foreigners who might have been seen as ghosts and the … need to try and achieve some level of communication in whatever form," he says.

"To be able to try and understand the context of that first interaction it's like a metaphor for things that continue to happen today.

"How is it that we're not communicating to the extent we're capable of today?"

Opening up those lines of communication and hearing stories from the places where the objects originated to give greater context is a key part of the Encounters project.

Many of the items featured in its twin show Enduring Civilisation which closed at the British Museum in August, but about 40 objects will only be seen in Australia.

People from 27 Indigenous communities across Australia were consulted and interviewed over several years and the reflections of about 200 will appear as videos in the exhibition to give them a voice, the National Museum's director Mathew Trinca says.

He expects indigenous and non-indigenous audiences alike to be captivated and moved by the "most important work" the museum has done since it opened.

"I think many people when they come to museums are coming to see things they imagine will transport them back in time and there's an aspect to these objects that can do that," he says.

"But … more importantly is to realise how important these things are to Aboriginal and Torres Strait Island communities today."

Despite the optimism and excitement there's also a lot of "sorry business" surrounding the exhibition, reference group member and local Ngunnawal man Adrian Brown says. Namely the complex and sensitive question of whether the objects should return to Australia for good.

"I know a lot of the communities will want the items from the British Museum to stay," Brown says.

"[But] I guess this is the first time the British Museum has ever offered that opportunity for the Australian community to see those items so it's a step forward for everybody."

He hopes the project will spark some "genuine discussion" between the British Museum and the communities and eventually the "good rapport" could help get some of those items back.

Intervention to keep the items in Australia during the four-month exhibition looks unlikely now the National Museum has been granted extra legal protection.

The federal Protection of Cultural Objects on Loan Scheme, to shield loaned cultural objects from seizure and suit, was introduced in early 2015 but only approved for the museum in September in time for the objects' arrival.

Ned David, the chair of the Magani Lagaugal (Torres Strait Islanders) Native Title Corporation and also co-chair of the federal government's Advisory Committee for Indigenous Repatriation "finds it interesting the federal government moved so quickly" with the new laws, but like many of the Indigenous people involved is reluctant to get into the debate over the objects' permanent return, preferring to focus on the positives of the project.

Trinca says the British Museum agreed to loan the objects in 2007 before the added protection had come in place.

While he "can't predict the future" he too remains hopeful about future "dialogue" and says British Museum director Neil MacGregor was courageous for welcoming the repatriation debate "between friends".

"I support Indigenous people's rights to make whatever argument in their interests around these collections," he says.

"The alternative would have been to do nothing and leave these collections where they were at the British Museum, but I think that's a path that wouldn't have been in the service of Aboriginal and Torres Strait Islander people nor in the interests of all Australians."

He says as the collaborative project matured many people turned from the question of repatriation to access, whether digital or in the flesh.

In any case the opinions of Indigenous people involved differ. Some look forward to seeing the objects; others are distressed at the thought of their return to England.

The origins of how each of the objects was acquired are also diverse and in some cases uncertain.

Yu says the new laws put the onus on the lending cultural institution to ensure there is evidence to support the objects' provenance.

"That in itself will create debate … about how was the material gifted: was it stolen, was the transaction equitable and reasonable – all those questions come up," he says.

David's great-grandfather Maino gave several items to Alfred Cort Haddon, a British anthropologist who first visited the Torres Strait Islands in 1888.

A headdress will appear in Encounters, but a mask in the British Museum Maino had specially made for Haddon to proudly show off Torres Strait Island culture in England is too fragile to make the journey.

"A lot of us feel when they donated these things it was for a purpose, and it was given with consent and we're happy for that," David says.

"We believe they were done under a mutual arrangement between Maino and Haddon, it's not for us to go and change that, [but] of course that's only restricted to these things."

The issue of repatriating human remains and secret and sacred objects is a "whole different kettle of fish".

"The British Museum are the biggest bastards at the moment that I'm dealing with on that topic, but that's a different fight all together," he says of his work on the repatriation advisory committee.

"For all the great things we are doing together with this project I'm hoping they can demonstrate a bit of altruism or some sense of morality or humanity about the separation between how you treat human remains to these things which are artefacts and objects.

"But in between all of that there are secret and sacred objects, which is totally different."

All hope the project will help pave a way forward.

Trinca says the exhibition, and an associated conference in March, will force museums and galleries to confront how they should handle cultural objects in their custody from around the world.

But the project will also have a concrete legacy, in the shape of the many contemporary objects which will remain in the National Museum's collection.

Brown says he is "overwhelmed" that his painting showing his cultural connection to land, clap sticks bringing together song, law and ceremony and a shield telling his story with local ochre, will be preserved a long with the video testimony of about six local Indigenous people.

"As a young man growing up I was always looking for more material about Ngunnawal country and how to learn more," he says.

"With modern technology we have this opportunity now through the museum to have those stories recorded for our future."

He believes the appetite and interest in Indigenous culture from both the Indigenous and non-Indigenous has increased.

"I think the environment's changed in the last five or 10 years where people seem to have more of a hunger to learn about local Ngunnawal culture, but also nationally they want to learn more about Aboriginal people and connection to country, their fire and land management practices," he says.

Trinca says non-Indigenous did not look to other cultures elsewhere, for sustenance and delight.

"We look within to honour the singular truth that we live in a land home to the world's oldest human tradition," he said.

"It's about bringing those cultures and traditions into an honoured mainstream society and a continuing view about the strength of this nation being built on its Indigenous traditions and cultures, on its British foundations and institutional frameworks, and on the truth of our plural multicultural community that is the chief characteristic of Australia in the 21st century."

But Yu says it can still be difficult having gravitas and eliciting an emotional response from Australian society.

He is hopeful the objects, like the shield collected by Cook, will prompt a connection.

A small stone scraper, the only British Museum object related to the local Indigenous population, is an example of how the culture lives on.

William Kinsela collected it from Mount Ainslie in 1932/33, but Brown says it remains a site where Indigenous people take their young people to point out the regions of Canberra and teach them the original names.

"There's a sense of pride that our communities are still practising that ancient culture," he says.

Encounters is on at the National Museum of Australia from November 27 to March 28.