T H Robsjohn Gibbings? Widdicomb? McCobb?  

Interesting. I own a John...
Interesting. I own a John Stuart Cligman spindle back chair from Widdicomb. Those back legs are identical to mine. The curve of the back leg is distinctive.
If there is no marking, it's a bit odd. But guess it could have come off if reupholstered at some point. My Widdicomb chair had markings and labels on at least three points. A label on the cushion, a label underneath the cushion on the chair seat, and two labels underneath the chair.
Links to photos of my chair here including various labels. I wish I could take pics of the back legs for you...but it's undergoing upholstery process now.
http://www.pinterest.com/kiwimberly/mid-century-widdicomb/

p.s.
Looking at the chairs a...
p.s.
Looking at the chairs again...
I really think these are Widdicomb and were reupholstered in the 80's. That's an 80's fabric. If they redid everything, including the horsehair inners, they might have managed to remove even the labels on the very bottom underside of the chair.
The wood on Widdicomb is distinctive. It's like Heywood...you can't miss it. I'd be surprised if these were something other than Widdicomb.

agreed
i've owned and sold a few and they very very much have the right lines.

they might be Metropolitan.........
I have in the past come across two sofas with those dowel details and proportions bearing original Metropolitan labels.
Everyone told me that they were Mccobb or Gibbings but the label said Metropolitain.
I looked for an image but sorry was unable to locate one.
Good Luck!

Not McCobb
Though I cannot say exactly who did make these chairs I can put to rest the supposition that they might be by Paul Mccobb, they are not.
http://paulmccobb.blogspot.com

This came up on Facebook today. Here is the answer. Kudos mario.
https://www.1stdibs.com/furniture/seating/lounge-chairs/sculptural-teak-...

I have a Metropolitan Cube chair in oak and Wool that I really love. Never found out anything about the company. They seemed to make really high end stuff.

Jules Heumann is the name I always see associated with the company as their designer. I don't know if he designed everything metropolitan.
I have a few of their models documented in a California Design.
Are the legs actually teak? That would be pretty rare.