Length: 12 cm.
Presented on a later support.
Many replicas of this highly coveted relic were made over the centuries. This example is one, dating from the 19th century.
According to legend, Saint Helena (mother of Emperor Constantine) had the site of Calvary in Jerusalem excavated and miraculously discovered the relics of "the Passion of Christ" on May 3, 326 1.
In 549, the cult of the Nails of the Passion was recognized by the Church 2. The first testimony we have of the relic of the Nails is apparently that of Saint Jerome (340-420). Then many relics belonged to famous people as well as pilgrims, over the many centuries 3, and in many holy places.
Historical texts relate that Philip V of France (1291-1322) was cured of quartan fever by touching the Holy Nail 4.
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Bibliography:
1 - ED Hunt, "Constantine and Jerusalem", The Journal of Ecclesiastical History, vol. 48, no 03, July 1997, p. 415
2 - Frolow A., 30. See Migne, PL, LXVII, col. 1229.
3 - https://prosamor.wixsite.com/reliquesdelapassion/la-relique-des-clous#_ftn1
4 - Collin de Plancy JAS, Dictionnaire, tome I, p. XLV.