Are these Nakashima?  

Interesting
Do you have a photo of the underside? Any markings?

Unfortunately these are the...
Unfortunately these are the only photos I have. They are a number of hours away, so I'm not sure if I should buy them or not.
I have a feeling there are no markings, because other items listed have manufacturer or designer names listed in their descriptions, ya know?
But regardless of buying them, I'm interested if Nakashima ever make variants like this. It seems like it'd be relatively easy to put together your own Nakashima-esque table like these, though that bow tie would seem to require at least a bit of skill. So, I'm a bit puzzled.

Nakashimaesque...
I'd leave them be if I were you. The legs of the coffee table don't display the angle which give the splay table its elegance. That along with the hour glass and smaller versions means you're obviously looking at reproductions or interpretations here.

..
knoll? Somewhere online there is an article with drawings of his production range, will try and find it. The key does seem an affectation though and why is the top a glue up when two wide quartersawn boards would do?

Nakashima used
the butterfly key for functional reasons, not decorative ones -- it's a fine way to keep two pieces of wood from moving, relative to each other. The fact that it appears as a centered accent, here, can mean only that the maker wishes us to be reminded of Nakashima. . .