Oh, this is just one of them; there should be two other keyholes. When the three medallions of the Founding Patriots are reconfigured into their true form as Keys of Genesis and inserted in these keyholes, they unlock the way to the Path of Radiance, at the end of which is a power capable of turning back the Antichrist.

Although, it’s hard to tell from the photo; if it’s brass, not copper, then it’s just an old furnishing anchor.