A MYSTERIOUS identification card could be the answer to the 63-year-old mystery of the unknown man, discovered dead on Somerton Beach.

The case has intrigued investigators, code sleuths and amateur detectives for decades, but a picture of a British man named H. C. Reynolds on a 1918 US-issued seaman's identification card has now been positively identified by a facial recognition expert.

Internationally renowned anatomist and biological anthropologist Professor Maciej Henneberg, of Adelaide University, has used his expertise to compare the 18-year-old man in the card photo with police file pictures of the dead man.

"It's not just about an exact image," he said. "There is a close similarity of the ear, and ears don't change.

"The ear is a very good match, and there are anatomical similarities in other features."

But it is a mole on the cheek that cemented Prof Henneberg's opinion that it was more than likely the same man. "Such moles change little with age, though size may slightly differ," he said. "Together with the similarity of ear characteristics, this mole, in a forensic case, would allow me to make a rare statement positively identifying Somerton man as H. C. Reynolds."

An Adelaide woman, who did not want to be identified, found the card last year among old photos and documents belonging to her father, and took the card to Prof Henneberg after seeing publicity around former detective Gerry Feltus's book The Unknown Man. Mr Feltus wrote the book based on his investigation of the case during his career and published it last year.

The woman contacted the Sunday Mail after seeing a story about an unsuccessful application by Professor Derek Abbott, also of Adelaide University, to exhume the body.

Using mathematical formula and accounting for differences in age, angle, photographic distortion and facial expression, Prof Henneberg found the rare ear shape shown in both photographs made it likely they were the same person.

He also found that a mole that appears in both photographs was likely to be the same - which he calls a "unique identifier". Searches by the US National Archives, UK National Archives and Australian War Memorial Research Centre - at the request of the Sunday Mail - have not uncovered any records relating to the H. C. Reynolds in the ID card.

Prof Henneberg is considered an expert in the highly specialised field of biological anthropology.

He has worked for police and defence lawyers and is regularly called as an expert witness in court cases where identity is an issue.

Prof Henneberg said there were many difficulties in comparing facial structures from the images. Pictures of the Somerton Beach man were not taken until a few days after he died.

Prof Henneberg said that meant his face would have changed shape from before his death, with gravity altering the appearance of his cheeks, chin, eyes and forehead. But there were two indicators that helped him compare the photographs and come to his rare conclusion. The ears were of the same type and are the least likely part of the face to change with age or death.

Accounting for photographic differences, the nose, lips and eyes also appeared to be of the same type.

H. C. Reynolds would have been about the same age as the unknown man. The ID card records his age as 18 in 1918but the unknown man was believed to be in his mid-40s when he died in 1948. Prof Henneberg has passed on his finding to SA Police.

A spokesman said Major Crime was investigating the information.

Can you help unravel this mystery? Contact watkinsem@sundaymail.com.au