Teak 3 Seat Sofa ID (Wegner or Jalk Style?)  

Looks like a tinted lacquer...
Looks like a tinted lacquer finish to me, probably done to make a blonde or light colored hardwood appear more like walnut. There is nothing about the photos that remind me of anything made of teak.
Selig used a tinted lacquer finish like this for many of the beech Danish manufactured pieces that they imported for the U.S. market. I am not familiar with ever seeing this piece in a Selig catalog though, and it looks in some ways suspiciously like something made in America. American manufacturers from the period were also very fond of using tinted lacquer to impart the appearance of walnut.
Because tinted lacquer is only a superficial layer, it shows edge wear quite badly, since the lighter colored wood underneath becomes exposed as the finish wears away. It is not a very elegant way of finishing fine furniture. The brown dyes used also tend to turn a greenish color with exposure to sunlight, as in this image of a Selig chair with bad UV damage to all but the areas protected by the cushions.

I agree with everything that...
I agree with everything that tchp said. If given the choice between Selig's walnut, teak, and stained beech options, I would go for the first two almost every time.
However, the majority of Selig lounge chair options that pop up for sale tend to be stained beech. If you waited for solid walnut in a certain design, you could be waiting for quite some time, and then paying a premium for them. I have a few stained beech pieces by Selig and France and Daverkosen. While I wouldn't buy any new stained wood pieces, these 50+ year old stained guys have grown on me.

Selig's darkly stained beech...
Selig's darkly stained beech chairs are often described by dealers and on Ebay listings as "walnut" or "walnut finish", but in the Selig Danish Collection catalogs this finish was called "Saddle". Selig offered options for Teak, Walnut, Saddle, and a black ebonized finish they called "Nubian", which I believe only appeared on a very few items. I am sure the teak and walnut furniture cost quite a lot more. Few buyers in the U.S. seem to have opted to buy them, and the saddle finish is much more common, as cdsilva was saying.
I have seen a number of beech pieces by France & Daverkosen that I had always assumed to be in a natural finish, and was not aware of any that were actually stained?

I can't speak for the full...
I can't speak for the full range of wood options for fd pieces, but my Ole Wanscher settee is beech with what appears to be a teak stain. If oiled beech naturally darkens over the years to resemble teak, then perhaps it is not a stain after all. I do know that the wood inside the keyhole joints is much lighter than the surface finish. I have also seen old beech Wanscher chairs of the same design style which are still the natural light beech color.

My Selig Kofod Larsen chairs...
My Selig Kofod Larsen chairs that I am currently re-caning are stained beach. This is clearly evident on the backs when the cane was removed.

I just remembered that the...
I just remembered that the seat back frame for my Hvidt chair by France & Daverkosen had side rails that are made of beech stained to match the color of teak. I think they stained them so that if the wood could be seen peeking out between the wraps of the rattan, it would look like it was teak, and not a light colored wood. The exposed, visible parts of the seat on the top and bottom are done with teak of course.