There could be dozens of controlled tests possible with the many relics of Santiago in Europe. Santiago wasn't the first town to claim a relic of Saint James - various relics had been around for almost 300 hundred years before he was identified in Spain. So far I have been able to find three whole bodies and fifteen heads, two pieces of heads, a number of arms, hands, fingers and other limbs.
According to Prof. Leyser, an arm of James the Great was preserved in Torcello near Venice from about the 6th Century. It passed through the hands of Bishop Vitalis, and then Germany via Archbishop Adalbert of Hamburg-Bremen, the Emperors Henry 1V and Henry V. In 1125 Henry V’s widow Matilda brought the left hand of Saint James to England.
In his book “The Cult of Santiago: traditions, myths and pilgrimages” (1927) the Rev. James S. Stone writes about the many relics of St James found in Europe.
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In addition to the body at Compostella, a body in St. Sernin at Toulouse and another in the church at Zibili near Milan are equally authentic. There are two of his heads in Venice - one in St. George's church, and the other in the monastery of St. Philip and St. James. A head can be found in Valencia, a fourth head at Amalfi, a fifth head at St. Vaast in Artois as well as part of a head at Pistoja. In the Church of the Apostles in Rome are preserved a piece of the Apostle's skull and some of his blood. There are bones, hands, and arms in Sicily, on the island of Capri, at Pavia, in Bavaria, at Liege and Cologne, in Segovia, Burgos and elsewhere.”
According to Armenian tradition, the head of James the Greater is buried in the church of Saint James the Less in Jerusalem and only his body is in Santiago. On the left side of the church, opposite one of the four square piers supporting the vaulted ceiling, is its most important
shrine, the small Chapel of St James the Greater. A piece of red marble in front of the altar marks the place where his head is buried, on the reputed site of his beheading. (Church of St James the Less in Jerusalem)
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In France alone, there were three tombs containing his body, nine heads and numerous limbs. In 1354 the Saint-Sernin basilica in Toulouse was home to the head and the body of St. Jacques le Majeur.”
www.saint-jacques.info/anglais/spotlights.htm
“In 1385 the body of St. Jacques was transferred to a luxurious arch-shaped church. It was the most magnificent reliquary of the church after that of St. Saturnin.”
http://ultreia.pagesperso-orange.fr/toulouse.htm
Even America has a piece of the true cross and a Sant Iago relic. St James the Less Catholic Church in Wisconsin houses a great collection of relics: “
The most precious relics we have are those of the true cross of Our Lord Jesus Christ and of St. James the Less, our Patron. Just a few of the other relics are: ….and St. James the Great, Apostle.”