Designed by Kopf in 75  

It strikes me as the work of...
It strikes me as the work of a regional craftsman, hobbyist, or local furniture maker. I also have a chair by a regional furniture maker, Elliott Grey of Eugene, Oregon, USA. He was an assistant/intern of Arthur Espenet Carpenter in the 1970's.

Hmmm...
Definitely a first for me. Can't say I'm familiar with the designer.
While my first impression of the chairs is positive, I think I like the idea of the design more than the execution. It's not often I come across something that is markedly different, to my eye anyway.
The back and seat are very nice. But the legs are just a bit silly I think. Both the thickness and the angle put me off. It's as if the designer overthought or was trying too hard to impress. Didn't come off in my opinion. A simple straight tapered leg design would've yielded a really lovely chair.

What lunchbox said
At first glance, I thought they were kids' chairs. They have a heaviness that would look ok if they were 3/5 the size of regular chairs.

Possibly the work of Silas Kopf.
You might ask him?
http://www.silaskopf.com/silas_kopf_biography.htm

Other than than the...
Other than than the upholstery, I think they are really nice. I've got no problem with the legs or proportions. To my eye, beautifully executed.

A bit clunky, perhaps,
but very much in keeping with the organic style popular with American studio furniture craftsmen at the time.

Silas Kopf
I have contacted and he said they are not his. He was not sure who it might be.
FYI the Table is also solid teak and signed by "Lockwood" in 1973

I've got a few references at ...
I've got a few references at home that feature studio work of this nature from the '60s and '70s. Will take a look when I get home and see if anything turns up.

Hmmm... well, it's possible
that these items haven't travelled too far afoot. If you're really curious, you might try sending the photos around to local long-established dealers, auction houses, craft schools, and/or galleries that feature one-of-a-kind furniture. Often, though, many of the less successful folks didn't produce much before moving on to more lucrative pursuits.
Jesgord, those annual "Design" books from that period published by Fine Woodworking Magazine and Taunton Press would be one of the first places I'd look.

The wood type was striking...
The wood type was striking me as looking a lot like walnut.

Finally had a chance to look...
Finally had a chance to look through my books on studio woodwork. Sorry, no luck on Kopf.

Was looking through...
Was looking through "Creating Modern Furniture" by Dona M. Meilach (Great book on wood studio furniture). Cam across a maker named Al Lockwood. Mostly worked with laminated woods (not solids) but you never know. Thought it was worth a mention.
I think most, if not all the pics in the link are from the book
http://mondo-blogo.blogspot.com/2010/10/i-know-you-were-stoned-when-you-...

Wow is right!
Great link Jes.

Great Spelunking. Hardly... Great Spelunking! Hardly seems like a coincidence. Now to find more on Lockwood. Thanks Jesgord