The project chair  

Glide issues
Well I just tried to get the glides out and they won't even budge....the turn but don't come out. The one missing there is a long smooth shaft...no threads. Also found an interesting stamp on the inside of the plywood. Looks to be dated March 1964.

Welt is easy to make yourself.
It's basic upholstery, just cut strips of leather and wrap them around welt cord and sew with a welt (zipper) foot. With leather you can glue instead if you prefer.
Try the link below for glides.
http://swivel-chair-parts.com/EamesPlycraftAvailablepart.html