https://www.st-marks-basilica.com/about/
[snip] History of St. Mark’s Basilica in a Nutshell
In 828 AD, two merchants left for Alexandria and visited the St. Mark’s sanctuary that held the Saint’s body. On their visit, they spoke to some of the custodians of the sanctuary who told them that there were talks about demolishing the sanctuary. Hearing this, the merchants want to preserve St. Mark’s body and rescue it in Venice. They hid the body under pork and Alexandria being an Islamic state considered pork haram. This made it a smooth entry into the country.
On reaching Venice with the stolen relic, it was temporarily kept in a chapel within the Doge’s Palace for the initial 2 years. It was then restored to its present home by Doge Domenica in 1071. [/snip]
a key claim by the researcher is that the measurements of the masonry piece in venice (clearly macedonian) suggest it would precisely fit the sarcophagus of (forget his name) the emperor who was expelled when alexander conquered egypt and historically was always said to have been used for alexander himself.
the church will not allow any dna testing on the relics, of course (they never do). but it is an interesting topic.
the stories of how st mark died would seem to preclude his own actual body being available.