I know some christians that are convinced that we have the exact pieces of cross that Christ died on, being kept preciously somewhere in the Vatican with other items that may of belonged to the Christ himself. I am a bit skeptic since I didn't find any reliable sources on this question. Could that be possible? Thank you for your help!
Edit: added a "be".
Historically, relics were a big business to medieval churches. Having the bones of a saint made pilgrims come to your church and perhaps offer donations. Having a religious relic could potentially see you get enough money to build a cathedral.
As mentioned already there are some 8 nails all claiming to have been used in the crucifixion. One of these nails is part of the "Spear of Destiny" in the Austrian collection in Vienna. That spear is one of 4 all claiming to be the one used at the crucifixion.
Even more bizarrely there have been over 15 different objects claiming to be the Holt Prepuce or the foreskin of Jesus.
My personal favourite, though not relating to Jesus, was the cult of Thomas Beckett. After Beckett was killed in 1170 monks of Canturbury Cathedral soon started selling small bottles reputedly containing the blood of the Martyr Beckett. Sale of these ampules continued into the 16th century. Not a bad run from blood soaked off the floor from a head wound.
None of the artefacts reputed to be associated with Jesus have ever been scientifically tested as authentic
As a follow-up question, there are "artifacts" in the Istanbul Topkapi Museum, no less, that purport to be objects belonging to prophets, such as the footprint of Muhammad in stone and the staff of Moses. These seem very unlikely to be genuine, so where did these artifacts come from?