Urgent help needed - Steelcase or Knoll?  

I have now seen the receipt...
I have now seen the receipt where they are referred to as Model 65 AC (the chairs) and Model 67 AC (the sofa), everything looks in order.
Contacted the author of a heavy Knoll volume who was kind enough to answer - he could not give me a definitive answer but was convinced they were Knoll.
I have gone through every picture of the models I have been able to find online and have to say that apart from the upholstery job they look identical..
I'm leaning towards believing this is the real deal but would love to hear if the skeptics in this thread are still convinced of the contrary?
Thank you.