It is one of the many phoney relics, which included the "true" cross, brought back from Jerusalem by Helen, the mother of the Emperor Constantine, in the fourth century...
Helen is an interesting character in her own right and the story of how she found the nails is amusing enough:
"
The emperor deeply revered the victory-bearing Sign of the Cross of the Lord, and wanted to find the actual Cross upon which our Lord Jesus Christ was crucified. He sent his mother, Helen, to Jerusalem, providing her with a letter to St. Macarius, Patriarch of Jerusalem.
Although St. Helen was already in her declining years, she set about completing the task with enthusiasm. Searching for the Life-Creating Cross, she questioned both Christians and Jews, but her search remained unsuccessful. However, in 326, she was directed to an elderly Hebrew named Jude who stated that the Cross was buried at the Temple of Venus. St. Helen ordered that the pagan temple be demolished. After praying, the ground began to be excavated. Soon, the Tomb of the Lord was uncovered. Not far from it were three crosses, a board with the inscription ordered by Pilate, and
four nails which had pierced the Lord’s Body
.
In order to determine the cross on which the Savior had been crucified, St. Macarius alternately touched the crosses to a corpse. When the dead man was touched by the True Cross of the Lord, the body came to life. Having beheld the raising of the dead, everyone was convinced that the Life-Creating Cross was found.
During the discovery of the Life-Creating Cross, another miracle took place – a grievously sick woman, beneath the shadow of the Holy Cross, was healed instantly. Elder Jude and other Jews came to believe in Christ and accepted Holy Baptism. Jude received the name Cyriacus and afterwards was consecrated Bishop of Jerusalem. "
http://www.antiochian.org/node/18634
Neither wiki nor the BM, of course, but the source I quoted has its own charm.
It seems the
Pasiong Mahal has mixed together several different versions of the fate of the nails used in the crucifixion, doesn't it?