[NYer]

What did Jesus look like? Amazingly, there is no description of Him in the New Testament or in any contemporary source.  Yet, in hundreds of icons, paintings, mosaics, drawings and coins, there is a common quality that enables us to identify Jesus in works of art. Shroud scholar and historian Ian Wilson theorizes that a common set of facial characteristics became the norm following the discovery of the Edessa Cloth concealed in the city's walls in 544 CE. 

Apparent Shroud-inspired images of Christ are noticeable on coins struck in 692 CE during the reign of the Byzantine emperor Justinian II. The distinctive front-facing appearance of Jesus on the Shroud is also found on numerous icons, mosaics and frescos from the sixth century on. The most startling example is the Christ Pantocrator icon at Saint Catherine's Monastery, reliably dated to 550 CE. 

the 1930's, French Shroud scholar Paul Vignon described a series of common characteristics visible in many early artistic depictions of Jesus. The Vignon marking, as they are known, all appear on the Shroud suggesting that it is the source of later pictures of Jesus.
 

• A square U-shape  between the eyebrows. 
• A downward pointing triangle or V-shape just below the U-shape, on the bridge of the nose.
• Two wisps of hair going downward and then to the right.
• A raised right eyebrow. 
• Large, seemingly "owlish" eyes. This may be the result of coins placed over the eyes.
• An accent on the left cheek and an accent on the right cheek that is somewhat lower.
• A forked beard. Dr. Whanger (see below) has suggested that this may the result of a chin band tied around the head to keep the mouth closed.
• An enlarged left nostril. 
• An accent line below the nose and a dark line just below the lower lip. 
• A gap in the beard below the lower lip. 
• Hair on one side of the head that is shorter than on the other side.
  

  
  Christ Pantocrator, c. 1200 from dome of Church at Cefalu, Sicily. 

  
  Computerized overlay of the Shroud of Turin facial image and the Christ Pantocrator icon from St. Catherine's Monastery (550 CE). Images were scaled to the same size and shifted horizontally and vertically for alignment. No changes were made in the vertical to horizontal ratios.

  
  This image is a computerized density average of the negative of the face and the Pantocrator icon above. The high degree of symmetry is best seen by changing the relative averaging weights of each picture which you can do with a Java Applet that runs in your web browser.

  See For Yourself at this link.

[Destro]

The Edessa Cloth concealed in the city's walls in 544 CE is I am assuming also the Mandelion, which vanished after the sack of Constantinople by the Latin Crusaders.

As for the Shroud of Turin, it may be authentic or it is probably an artistic recreation of the actual Mandelion, the way blessed icons are copied ad infinitum. The icon of the Virgin Mary was said to have been painted by St. Luke himself and from his hand do the representations of Mary come down to us copied over and over again.