Early 70's chair

I have acquired a pair of these Swivel chairs from a friend who was having to clear his Grandmother's house.
I think they are 60's or early 70's, but have no other information on them- so any insights that people have would be greatly appreciated!

The back of the chairs are a hard, moulded plastic.
The black padded seat is made from (I think) black PVC.
The swivel base is silver metal with a Star design.
There does not seem to be any other markings on the chair.

I have tried to find this model by searching the internet, but cannot seem to find anything that is exactly the same.

If anyone can shed some light on this mystery I would be really grateful!