A closer look reveals checkering on the face and sides of this piece, and some interesting engraving on the brass disc.

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I have a hunch that this is a valuable pre-Columbian artifact, used for calculating the distance to the stars. I bet it was some Viking guy who dropped it one night after a little too much mead.

 

Also, I've added a couple more lenses not shown in these photos. IE: It's even cooler now.