>>3452030
It's called the Eye of Providence.
official explanation:
https://greatseal.com/symbols/eye.html
alternative one:
http://www.ancientpages.com/2018/02/13/eye-providence-powerful-secret-symbol-deep-meaning/
If you take a look at it on the bill, seems pretty clear on what it represents in that context : the top floats above the bottom with the bottom providing support for the top, but not connected and thus blind to the ways things work from the top.