Arne Jacobsen 3217 desk chair  

Hi Addicts,
I've found an Arne Jacobsen 3217 chair on the internet that I want to buy.
But, a normal version of this type of chair, is, when in wood multiplex, only mounted on the underside or downside of the seating (wood) and you can't see anything of the mounting on the upper side.
The chair i've found has mounting on the upper side.
Maybe the chair was ever been upholstered with leather.
So I want to ask all the owners of that kind of chair to feel in the middle of the seating area if you can feel something like a bump.
Thanks in advance,
All kind of tips are welcome!
Best regards!
T