Why Can One See This Strange Object on All Ancient Artifacts?

It may be fake but what the hell is this? Is it a magical device, hidden by the science? Or, is it an allegorical symbol, a metaphor?
Doesn't it represent a lock of some kind? Why is it depicted with a symbol of pineal gland?
Are the creatures our overlords? Have they locked our pineals or they just symbolize telepathic communication between themselves?