dnd 5th – What does a "Gem of True Sight" do?

Could this speak of a jewel to see?

The jewel of vision offers a true vision.

According to the description of the module and the list of articles

"In my adventure, the priest, the witch and the lost temple, two new
Magic items are featured: the jewel of interdimensionality and the orb
from Undeath. "

Since this is not a module-specific element, it can be a typo.