After spending a century lost in the dirt south of Perth, a World War I military badge has been returned to the grandson of the Gallipoli Veteran to whom it was originally issued.

Hobbyist metal detector Matt Franceschini thought he had found an old coin when he unearthed Charles John Richardson's Return From Service badge last year.

It was buried under 20 centimetres of dirt in what is now a park in Perth's southern suburbs.

Charles John Richardson was shot in Gallipoli and sent home, before he re-enlisted and went back to the front. ( Supplied )

The chance find sparked a year-long search to trace its origins, which eventually led to Mr Richardson and his grandson Gary Richardson, who collected the badge this week.

In 1916, Charles Richardson went to war along with three of his brothers.

He was shot in the arm after just one week at Gallipoli and sent to England to recover, while one of his brothers died in the trenches.

In England, he contracted bronchitis and was discharged from the army and sent back to Australia where he was issued with the Return From Service badge in 1917.

The badges were given to soldiers sent home before the War's end so they could show they had already served and avoid being accused of cowardice.

Mr Richardson did not need that protection for long.

Within months of arriving back in Australia he re-enlisted and was sent back to France where he served as a tunneller.

He survived the war, then went on to have a family and passed away in 1954.

Matt Franceschini shows Gary Richardson where his grandfather's badge was found. ( ABC News: James Carmody )

Mr Franceschini said the badge was the most precious find he had made with his metal detector.

"That's the whole reason I got into this hobby, the history behind things like this just blows me away," he said.

"To think that someone lost it 100 years ago and then to piece together their story with the help of other people and learn what he went through, and the fact that I've found a piece of that history is just mind blowing to me.

"There is a lot of history around here, we don't get it like they do in Europe and other places around the world but there is a lot right under people's noses, you just have to do a bit of research into it."

Gary Richardson now has the badge along with his grandfather's military papers. ( Supplied )

Mr Franceschini said returning the badge to Gary Richardson was even more rewarding than discovering it.

"I was very surprised to receive a phone call about his badge, it was really thrilling, it takes me right back to stories about my grandfather," Gary Richardson said.

"It's absolutely amazing to find something that could have been buried all those years ago.

"I think he would be thrilled to bits that an interest has been taken in something that happened so long ago and has just by chance been unearthed."

Mr Richardson said he would now wear his grandfather's badge each Anzac Day and pass it down to future generations.