Using an electron microscope, they found that they could make out the letters "UCAI" on the coins(called leptons); the letters "UCAI" were part of a roman word that was only inscribed on coins issued by--get this--Pontius Pilate in upper Palestine between 29-31 A.D.
Though the lepta (plural of lepton) minted in Palestine were Roman produced coins, the inscription of Tiberius Caesar would have been written in Greek as TIBERIOU KAISAROS. Was the C, where a K was expected, a misspelling? This was a problem that seemed to preclude positive identification until an actual lituus lepton was found with the aberrant spelling. Several have since been found.
There will always be skeptics ... St. Thomas was the first. Thank you, HumanaeVitae, for the information on the book. I have not read it but will pick up a copy.
Wow! I've kept up with the Shroud over the years, but this piece of info is news to me... incredible discovery! Thanks for the name of the book "The Ressurection of the Shroud" - I just put it in my Amazon.com shopping basket.
The discovery of the figures in the Guadalupe Virgin's irises is incredible as well. Both the Shroud of Turin and the image of Our Lady of Guadalupe are gifts from God, IMHO.