posted on May, 9 2013 @ 09:31 AM
They look kind of like Gnomons to me.
Where the changes in the suns latitude in the sky
are marked by where the shadow falls
during different days of the year.
Of course Gnomons, or sun dials, are known
throughout the ancient world. The key for me
are the holes in the center of all four copper plates.
Perhaps there was one Gnomon and each plate was slipped over it,
to record shadows and then they could be removed and stored,
or retrieved and compared to the shadows on different days.
Sort of like a Read/Writeable disc of the ancient astronomers.
Even the Aztec Calendar stone
has these types of markings around the outside of it.
/my two cents