What design is this chair?  

Anymore pictures would be helpful! Any labels when you were reupholstering?

Look slightly like oak to me.

'60's might be pushing it. Chairs like these I would have expected to see in a doctor's office waiting area ca.1979. Vaguely "Scandinavian Modern" influence. If in US, you could safely just call it a "modern style contract-quality office chair".

Thanks! I purchased them at a thrift shop, soooo. I did think they had a mid century look to them at the time. Didn't realize that the picture was sideways so sorry for straining necks to look!