I just picked one up with a leather sling. I'm struggling figure out who might have made it and when. The leather seems of good quality, and the chrome isn't bad. In terms of details, philips screws hold the wooden arms to the metal tubes. The arm tubes have chrome caps on their exposed ends.
Can anyone explain the difference between the M,S and B? Is roundness of the ends of the arms a factor? Are there any reproductions/knockoffs of these chairs being made? Google doesn't seem to be turning anything up that isn't used or vintage. Some claim to be manufactured by Thonet, but not all.
Thanks,
Peter.
(edit:added a couple of pics) 
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