Roland Rainer rocking chair - confirmation  

I want to ask you for a confirmation or identifaction.

I know there is already a thread about that chair if it is designed by Tapiovaara or Austrian architect Roland Rainer.

For sure it is not Tapiovaara!

Dorotheum says it is Ronald Rainer:

https://www.dorotheum.com/auktionen/aktuelle-auktionen/kataloge/list-lots-detail/auktion/11484-herbstauktion-in-linz/lotID/695/lot/1957267-schaukelstuhl-entwurf-roland-rainer-um-1958.html

But I do not find any confirmation , a photo or a catalog if it is really Roland Rainer.

Attached is a picture with a stamp on the bottom of the chair with the manufacturer date "26.April 1965" and a logo "2K". Does anybody of you know this stamp?

Some attribution says that is was manufactured by Thonet bit I never saw a Thonet logo on that chair.

Or maybe the chair was manufactured in ex Yugoslavia?

Any hints or confirmation photos are appreciated.
<img class="wpforoimg" src=" http://d1t1u890k7d3ys.cloudfront.net/cdn/farfuture/GCI1J7-eTj_cH5fSGNZAk