Travertine coffee table - Bertha Shaefer / Walker Zanger  

Aha, Bertha Schaefer!
actually, I just answered my own question thanks to google. Found its mate and they're made by....Bertha Schaefer. See pic and link, below.
http://www.1stdibs.com/furniture_item_detail.php?id=565616

store label and date stamp
I just happen to have an immaculate version of this table with a store label label and date stamp. It is a beautifully constructed piece. Do you know what W.Z. stands for?

W.Z.
There's a company named Walker Zanger (established in 1952) that seems to specialize in travertine products (such as table tops)-- perhaps they made the stone tops?

Walker Zanger
You beat me to the punch. Walker Zanger is an an American company that specialized in Italian and other stone. A short article is here: http://www.allbusiness.com/mining-extraction/mines-mining-nonmetallic-mi.... Timeline makes sense for this piece.

Attributed by who?
The Bertha Shafer attribution on the 1stdibs listing is highly questionable. I independently researched this attribution some time ago and could find absolutely nothing in the historical record to support the claim.

Bertha??!
Straylight,
Very interesting caveat. I've seen the attribution elsewhere, but, I agree, nothing conclusive. You've probably seen them all as well, including this table with similar construction.: http://samkaufmangallery.1stdibs.com/itemdetails.php?id=431050
Schaefer's papers are apparently archived at the Smithsonian...may be worth a trip one of these days.
And if anyone knows of any more solid attribution...

Bertha Shaefer and M. Singer & Sons
M. Singer & Sons was a furniture manufacturer first and foremost. I take issue with Sam Kaufman's explanation that the furniture was designed by Shaefer and manufactured in Italy, this just plain and simple never happened.
There's also the issue of form. Shaefer's furniture designs are linear and angular, never once in the images published of her design work is there anything even remotely similar to this table in design or form. I will also mention that after further research it now appears that this particular table design has never once appeared at a reputable auction house as a Bertha Schaefer design.

Who produced and designed this form then?
I just bought this side table off of Craigslist with the same W.Z. label. So how should I be caring for the wood finish? I have scand oil, Howard's feed and wax, Howard's furniture polish, Pledge, 0000 and 000 steel wool. The table has had a collision or two with a vaccum on its legs and some spills on the wood that need to be cleaned.
I have also done some internet searching on my own also. I have seen the table sell as "Gio Ponti" style, "Kipp Stewart for Drexel", the generic "modern", and the generic "Italian".
So, if the table was made by Singer and Sons, it is American. The only label on most marble tops state made in Italy. I assume the combination of Italy and Singer and Sons is where the Gio Ponti attributions come from.
So where does the Kipp Stewart and Drexel attribution come from? That must be cataloged somewhere? Is that connection just pulled out of thin air? Who is to say who made the design and manufactured these tables?

I question the attribution
It would seem that unless there is a solid reference, the attribution is false but we have to always keep in mind that this is never a truth until we find a certain attribution to this particular table. I.e, lack of evidence of attribution is not evidence of no evidence.
I dislike straylights abruptness and sometimes over confidence in his attributions as he sometimes puts a foot wrong (rarely), but I think he is on the money on this one.
When comparing other Singer & Sons products one thing does stick out - the immaculate and well positioned dovetailing/connections where it counts.
On these Travertine tables the way the legs connect to the top brace is just not right.
I have a friend who has this entire set of end tables and the large round coffee table and the quality of how the wood is connected is just not up to par with Singer & Sons quality.
If you compare the woodwork and quality workmanship on how the parts fit together, this table just does not fit the bill.
I think straylight is right, because he knows and has studied the base references, and because from a design point of view, the way these tables are put together is not high quality - the connections are not top end.

I've had a set of fully marke...
I've had a set of fully marked Singer + Sons dining chairs that were piss poor quality wise.

OK
I haven't seen everything Singer & Sons did, and I am no expert, just commenting on what I have seen and compared it to those.
Just seems odd to me that such effort would be performed to have such a nice curve, and then be let down by a piss-poor joint like that, I've seen other Singer & Sons by some high end names and they seemed to insist on exquisite form all-round, but I guess that is why we see Signer & Sons for Ponti's table going for many thousands at the major auction houses, and this one does not.
And to moderate my comment on straylight, I guess the poem partly quoted below is a good example of how newbie collectors and wishful ones are taken with the bad news...
"But I, being poor, have only my dreams;
I have spread my dreams under your feet;
Tread softly because you tread on my dreams."
🙂
Go easy on them.

I have the Singer & Son catalogue
and that table does not appear anywhere in it. Nor does the wood look like the italian walnut that was used on most of their tables.

Sent an email to walker Zanger
I sent an email to a rep at Walker Zanger to see if the logo was theirs.
You never know.

It was produced by Gordon's Fine Furniture of Johnson City, TN which incidentally produced quite a bit of "Italian style" or "Ponti style" furniture.