>Is that the underside of a wheel seen behind him leaning against the wall? It kind of looks like the same circumference so maybe that is what the bottom looks like and might help in figuring all those questions out.
... and could the bottom pivot be standing in-front of the that wheel (like an upside down thumb-tack).
Could be a very nifty way of getting the centre of gravity of the wheel below a single pivot point,
and most of the mass at the circumference.