Knoll Tulip Table fake?  

Post pics of the table

screws
A lot of the knockoffs have visible screws through the top of the tulip base into the underside of the table. That's the quickest way to tell.

Knife Edge
Almost all of the vintage knock-offs have a rounded or squared off edge. Knoll's has a beautiful deep knife-edge bevel on the underside. You can see it in the photo below.

This is one of those creations
where not one knockoff variant is worth anything to me. All of it is absolute garbage.
If you don't get an honest Knoll Tulip, pass it by.

The early Burke copies are...
The early Burke copies are quite nice. I have one inherited from my grandparents, virtually indistinguishable from the original unless turned upside down, exposing the telltale screws.
Without a doubt, the originals are better as a whole vs copies.

Burke vs. real
I have an aluminum Burke base that I like a lot. I couldn't tell the difference between its shape and that of a Saarinen until I saw the two side by side. The Saarinen is more graceful, and I was told that it doesn't tip as easily as the Burke. I don't care---I like my Burke. The top has a nice edge, too. I hate the square-edged ones.
I do have a real Saarinen in the small end-table size.