Amtrak chair from 60s or 70s miller? knoll?  

Hi

I get asked about once a year who made my favorite occasional lounge chair. I pick up on my google search but always come up empty handed. Can you help me id this chair's designer and/or producer?

I purchased it at a yard sale for probably $30 in Phoenix 10 years ago. Seller noted it was from the 60s but I've thought it more from the 70s. The only identifying mark on it is an Amtrak property sticker on the back (see pic). I'm assuming it was recovered but maybe not given that sticker is still there. I found this article that referenced Amtrak purchasing three new chair styles (in 70s?): Herman Miller LaFonda chair and the Knoll Morrison-Hanna chair - but they don't list the third type.

https://history.amtrak.com/blogs/blog/creating-a-visual-identity-the-amtrak-standard-stations-program

I love it and would love to tell people who it's by when they ask.
<img class="wpforoimg" src=" http://d1t1u890k7d3ys.cloudfront.net/cdn/farfuture/GIXMAgeqnJG7wW8wXMIN44