Need help identifying this barcelona stool.  

Hello everyone, 

A while ago i bougth an old barcelona stool frame. I bougth it through internet and before i received it i was 100% sure that it was authentic Knoll but when it arrived i had second thougths. Everything seems to be perfect. The curves of the frame, the X section, the holes for the screws, the dimensions of the frame and the dimensions of the steel bar are the same  as the dimensions i read in a MoMA catalogue that i have. Everything looks perfect exept one thing. I believed  it was made from stainless steel. I did the magnet test and it is magnetic. Then i read online that some grades of stainless steel can be magnetic. The frame is old, i don't know when it was produced and what kind of stainless steel Knoll used to use back then. Afterwards, while i was cleaning the frame i noticed that there was something like peeling on one leg so i thought that the frame might be chromed plated but all the other details of the frame are characteristics of the stainless steel version. I read online that Knoll shifted from chrome to stainless steel in 1964. Can anybody tell what it is going on with this frame?  I bought it at a very very good price so even if it isn't Knoll i have made a good purchase but i need to find out. If it isn't Knoll it is the best replica i have ever seen in my life. Thank you so much.