A Torbay coroner has "run out of ideas" in trying to identify a mystery skull found by fishermen off the Devon coast.
Coroners say the skull is from a right-handed man aged under 40
Coroners have tried the Missing Persons Bureau and DNA testing in a bid to try and identify the skull, found six miles offshore in July 2005.
They have also published pictures of the teeth in the British Dental Journal in the hope a dentist may recognise the dental records.
"This is as far as we can go," said HM Coroner Assistant Ric Parsons.
An inquest into the death of the man was opened and adjourned on Wednesday.
"We honestly don't know where the body has come from," Mr Parsons said.
"The body can get moved around with the currents and some of the ships moving up and down so it could be from anywhere."
The coroners believe the skull is of a man aged under 40, who is right-handed and possibly white.
They believe the skull had been in the water for up to four months before it was found by the fishermen.
"We've tried everything we can," continued Mr Parsons. "With such a limited amount of information we have to go on, it's very difficult.
"The only thing we know is there's no damage to the skull.
"There must be some family or friends who are not aware that someone has deceased."
Tests on the DNA taken from a piece of brain tissue lodged in the skull have so far proved inconclusive.
Investigators initially thought the skull belonged to 20-year-old Bruce Arcamo, but the tests ruled out this conclusion.
The Filipino ship officer is alleged to have stabbed and battered to death Captain Walfredo Banta, 34, before jumping overboard as their vessel, the Overseas Josefa Camejo, sailed through Devon waters last year.
Mr Arcamo's body has never been found.