Experts at the Centre for Anatomy and Human Identification at the University of Dundee have told police the dead man, discovered near Kyleakin on the Isle of Skye in September, is older that first thought.
A total of 24 names given to the police have already been ruled out from the inquiry.
Detectives brought in experts in forensic and craniofacial anthropology and human anatomy, who have said the man is aged between 40 and 60.
A Police Scotland spokesman said: “A further facial depiction has been produced by the University.
“It is an artistic representation based on information supplied by the Police. This image will hopefully lead to recognition from the public and assist the investigation. A depiction of a tattoo on the arm has also been produced.”
The body was found at about 9.10am on Monday 09 September last year.
Police have a reported sighting before his death at approximately6.45am the day before when a motorist driving on the Broadford to Kyleakin section of the A87 saw a man walking along the verge half a mile away from the Skye Bridge.
The man was walking towards the bridge and matched the description given including the rucksack.
The spokesman said: “Twenty four names have already been given to the police and all of these have now been ruled out from the inquiry.
“Police are in regular contact with missing people organisations and police forces throughout the UK and abroad.
It is now believed the man may be aged between mid-forties to early sixties, he has short dark hair, going grey, and a moustache.
His face and forearms are suntanned with freckles on his forehead, across his nose and on his arms.
The man is described as caucasian, 5ft 10in tall, of slim build, and weighs 13 stone (85 kg).
The man’s teeth are in poor condition. A number of the teeth on top and bottom jaws are broken or missing.
The spokesman said: “We believe that the man was left handed and that he was a smoker.
“On the left forearm there are two self scribed tattoos – the first comprising of a cross or ‘T’ symbol measuring 2 x 1.7 cm and the second a ‘G’ like symbol measuring 1.5 x 2 cm.
“When recovered from the water, he was wearing - brown ‘Atlantic Bay’ Body Warmer, blue
‘Everlast’ hooded top, grey ‘Everlast’ T-Shirt, dark blue ‘Burton Menswear’ jeans, leather ‘Levi’ belt, black ‘[email protected]’ boxer shorts, black ‘Patrick’ socks, and black ‘Nike’ training shoes
“On his left wrist was a - chrome ‘Sekonda’ watch with blue face, and blue/red ‘Help for Heroes’ wristband.”
The man was wearing a black and red ‘Reebok’ backpack which was visibly full. It contained - black ‘Lonsdale’ shower-proof jacket, two Pairs of black ‘Lonsdale’ boxer shorts, one Pair of black ‘Umbro’ socks, blue ‘Umbro’ t-shirt, blue with white Striped ‘Adidas’ tracksuit trousers, white ‘Lonsdale’ t-shirt, white Real Madrid ‘Adidas’ top, NY red and blue reversible beanie hat, pair of dark blue ‘Burton Meanswear’ jeans, black Celtic football top (with Carling written on the front), single Yale-type kKey attached to ‘Stanley’ fob, cigarette papers, cigarette filter tips, blister pack of Zydol 50mg capsules, and two Pairs of shoe laces.
The police spokesman added: “There are no suspicious circumstances to this death.
“If you know the man please contact Police Scotland on 101. Officers can quickly process names in relation to the inquiry so if you think there is any possibility the deceased is somebody you know, please get in touch.”