How to identify an original Noguchi coffee table?  

Look carefully
at the shape of the base pieces, and at the shape of the top. The base "breasts" -- the ends that are pinned to each other -- are just a little lumpy, and the top and bottom straight edges are just slightly concave, to prevent rocking.
The glass is quite thick. I believe it had a thumbnail edge in the early years; now it seems to be square, with bevels or rounding. Later ones are signed.
http://tinyurl.com/64xg4w3

That's brilliant
Thanks SDR.
It's always a bit tricky when some of these designs are now mass produced as replicas.

The signature on the edge of the glass is very recent.
A vintage table won't have it.

I'd like to see some vintage connecting pins.
This table is pretty easy to fake and I think I've seen more than a few attemps to deceive over the years.

The Glass
The glass is NOT symmetrical -which is what I see on a lot of copies. While the base is solid, I believe it has always been planked together from smaller chunks - much in the same way as the Eames Stools.

Most if not all
of the images on this page are of authentic tables. Study the various views carefully to familiarize yourself with the attributes of the glass and the base.
http://www.google.com/search?client=safari&rls=en&q=Noguchi%20table&oe=U...