About 7pm that day, an interstate tourist spoke to a man matching his description at Southport in the state's south, more than 300km away. 

Jason Sellese has been searching for his father since, using drones, sonar and divers to search waterways.

"We're just appealing for any information which could help us find him or his car," Jason told reporters on Monday.

"We think if we find his car we’re going to find him." 

Mr Sallese, who moved to Tasmania in 1961 after emigrating to Australia from Italy, had dementia and high blood pressure. 

A coronial investigation in 2012 said there was no evidence of foul play and concluded Mr Sallese died on or about the day he went missing. 

An inspector who reviewed case files said it was "remarkable" Mr Sallese's car had never been found. 

Tasmania Police district commander Stuart Wilkinson said missing person cases remained open until answers were found.

"The northwest coast is a tight-knit community. There are a lot of people committed to finding some closure for the Sallese family," he said.

Mr Sellese's car, a 2006 model, carried the registration plate FH2973.

Police believe he did not leave Tasmania and the Southport interaction was the last positive sighting of him.

Jason said he planned to search near a tip at Margate in the state's south in coming months after being told his dad was in the area about the time he went missing. 

He said the search remained statewide. 

"We’d like to be able to narrow it down, if not find exactly where he is," Jason said. 

"It would mean everything (to have closure). It takes a lot of our time. It would be good to put him to rest.

"We want to follow everything up. It might be the piece of puzzle that gives us an answer." 

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