Help Please - Authenticating Warren Platner Arm Chair  

Hi All!
New member to the forum - have recently caught the MCM bug, and am now hooked on designaddict! 🙂
I have recently come across a Warren Platner arm chair, in fair condition, and would love any assistance/pointers on how I can authenticate this piece? Unfortunately there were no stickers/markings in sight.
Of particular interest - if any member has this chair, and wouldn't mind commenting on how the seat cushion is attached to the chair, that would be great! I would estimate the chair I saw be from the 70s/80s, and it looked to be two simple velcro across the bottom of the cushion, attaching to a piece of plastic on the base of the chair?
I caught a good glimpse of the zipper on the back side of the seat cushion - pretty distinct in my mind, but should have snapped a photo!! If anyone can share a photo of the zipper pull, that would be wonderful!!
Thanks all!