Police are investigating whether historical coins stolen almost a decade ago from a former Northland museum are being sold on the internet.

Police have confirmed a Bay of Islands man contacted them and reported seeing coins, which he thought were part of the haul taken from Kelly Tarlton's Tui Shipwreck Museum at Waitangi nearly a decade ago, for sale on Trade Me.

Up to $500,000 of gold jewellery, coins and other relics recovered from the ocean floor by the late Mr Tarlton were stolen from a glass-covered vault on April 8, 2000.

Kitchenhand Keith McEwen spent more than seven years in jail for the robbery, but has never revealed what happened to the booty.

A $10,000 reward was offered by an insurance company for the return of the historical treasures, but not even that was enough to prompt a result.

The stolen haul included gold sovereigns that Mr Tarlton, a diver, had salvaged from the ship Elingamite, wrecked at Three Kings Islands north of Cape Reinga in 1902, and part of the Rothschild collection he recovered from the ship Tasmania, which sank near Gisborne in 1897.

A collection of greenstone and gold coins also disappeared.

The jewellery was not found and an insurance company rejected a $300,000 claim.

Widow Rosemary Tarlton was not getting her hopes up after the latest revelation.

Mrs Tarlton visited McEwen several times in Mt Eden Prison to try to find out where the stolen treasure had gone, but to no avail.

Speaking from her Auckland home yesterday, she said she hoped that the information would lead to the recovery of the stolen treasures.

"I've always felt it may come back to me. Because it was under the water for all those years and Kelly was able to retrieve them with lots of hard work and then they were stolen. They may come back again," Mrs Tarlton said.

Sergeant Peter Masters, of Paihia police, said a local man contacted police yesterday after he spotted what he thought were coins stolen from the Tui being sold on Trade Me.

McEwen is back in jail after pleading guilty to a high-profile attack on two Dutch tourists. He admitted a series of charges, including aggravated robbery, kidnapping, sexual violation and rape in November 2006 and received a sentence of preventive detention . The charges related to the abduction of a couple on honeymoon in the Bay of Islands. Justice Tony Randerson described the crime as "cruel and sadistic in the extreme". Co-offender Christopher Manuel received a nine-year jail sentence.