Digger's souvenir reunited with 'world's rarest tank'

Also awaiting transportation was German tank Mephisto. One of only 20 German AV7 Sturmpanzerwagens ever built, it was recovered from a battlefield in France and was being brought back to Australia as a souvenir of war.

It is thought Lt Lynch, in his position as an officer, helped himself to his own souvenir as the two crossed paths - a then-highly advanced compass that he took back as his own personal memento.

Mephisto would eventually be given to the Queensland Museum where it was put on display in the 1970s, but the compass was kept in Lt Lynch's family and passed down to his grandson Tom Lamin when he turned 10.

Over a century later, the compass has been reunited with the tank after Mr Lamin donated it to the museum.

"Tom sort of just had it in his garage gathering dust and (as a boy) used to do little experiments and things on it," Queensland Museum's senior curator Liz Bissell told AAP.

"And then he started putting things together, because his grandfather had always told him it was from the German tank at the museum.

"I think Tom must have sort of done a bit of research and realised, 'oh, grandpa', the museum has the only surviving example of the German tank in the world."

Mephisto had been on the forecourt of the museum in the 1970s and 80s, climbed all over by visitors.

But when the museum moved it came inside and since 2018, it has been the centrepiece of an Anzac Legacy gallery marking the centenary (with a strictly no-touching policy).

"We didn't even know it existed," Dr Bissell said of the compass that Mr Lamin donated in 2022.

"We had to do all of our due diligence and our research into whether it was possible that the compass was actually the one originally set into Mephisto."

Lt Lynch was in the right place at the right time, would have had access to Mephisto as an officer, had studied mechanical engineering before the war and would have been interested in the technologically-advanced magnetic style, floating compass.

And he had told his grandson all about the tank where it had come from.

"We are 99.9 per cent sure that this is it," Dr Bissell said.

The reunion of the pieces is a reminder that every story in history has many moving parts, Dr Bissell said.

"(The tank) is such an evocative object. It's got shrapnel damage, bullet holes. There's even soldier graffiti," Dr Bissell said.

"It was quite a crude design because it was one of the first tanks ever designed. They used to stuff like, 18 to 20 soldiers in there with two huge engines in the middle exposed and the soldiers just sitting around the outside.

"It's got quite a place in the Queensland cultural imagination ... a lot of people have really strong emotional associations with it. And we learn more about it all the time."

Other souvenirs taken by soldiers and on display in the Anzac Gallery include Egyptian scientific objects and amulets, pebbles from Gallipoli beach and bits of shrapnel and gauze.

There's even a German fob watch "which may or may not have been taken from a dead body", Dr Bissell said.

"I guess the soldiers felt like they had to keep talismans and things for luck on them as well," she said.

"They brought a lot of souvenirs back."

Australian Associated Press