I think this would be a good time to show some of the indicators that give away a fake.
Here's an image from the OP listing
(https://i.imgur.com/rQthScZ.png)
It's supposed to be from~1750, but it's spotlessly clean, including the wax seal and the string!
Also the fine print
EBay policy prohibits the sale of human remains and requires a disclosure of what the relics are: these relics are a piece of wood, which are allowed by eBay
Fake vicarate seal
(https://i.imgur.com/7DuDT9m.png)
Likely authentic seal
(https://i.imgur.com/PVDzh4L.png)
The Vicarate of Rome only distributes canonized Saints. The postulators of the various orders, were charged with the cause of the canonization of a saint. Depending on the time, the postulator of the order of the Saint may have distributed authentic relics: thus the relics will bear the seal of the particular order. The Seal of the Vicarate of Rome is not consistent from century to century, though it is similar to the above. Sometimes it has an even more square shape. While a light strike may be an attempt to cover up a poor stamp, a nice strike of the Vicarate of Rome seal is NOT indicative of an authentic relic, because counterfeiters have been much more careful to counterfeit this seal. Blackened soot marks are often present in genuine relic seals. Cracks in the sealing wax are only indicative of age. Cracks in the seal definitely can occur in larger old Thecas. 19th century Saints, or groups of Saints, with cracking seals, may be a good sign.