The Portuguese Templar Theory
Episode Four of Season Three featured yet another theory that ties the buried treasure with wealthy Christian monks. The team met with historian Terry Deveau, who informed them about a large carved boulder known as “the Overton Stone.”
Source: Reddit
Deveau believes that the stone carvings could be 500 years old and were made by a group of knights who traveled to the region from Portugal and (possibly) buried their treasure on Oak Island. According to Deveau, the cross on the stone looks like that of the Portuguese Knights of Christ and not like the symbols related to the Knights Templar from England and Scotland.