bruno mathsson pernilla chair..  

Do you have photos? I've seen chairs that look really similar but it's usually pretty easy to tell copies from the real thing just by comparing photos.

Hi thanks..here are pics

Well, right off the bat, the shape of the top of the arms is different from any genuine Pernilla chair I can find (see photos).
The pad is also very different---much flatter and the side padding is missing, though this could be a replacement made later by someone. BUT, yours also has two extra snaps at the top back edge, the corners of the webbing are not bound in contrasting leather, and the webbing doesn't have the three tucks at the seat/back curve that all the real ones have.
Oh, and the wood is not the color of beech, not even of beech that has darkened with age.
The shape of the arm is the strongest indicator, though, since all that other stuff could have been changed at some point.
Tip: 1stDibs dealers usually have a lot of good detail shots, making comparisons like this super quick and easy to do.