Wood and leather swivel office chair

Wood and leather old swivel office chair.  Bought at an antique store here in Johannesburg, but the store minder could not tell me anything about the item.  I pad R550 for it, which is roughly $55. I bought it because I like it, not because it may be valuable. 

But I would love to know more about it and cannot find anything similar to compare it to online.  Is it a captain chair, or a barrel chair, or something entirely else?  Which decade may it be from?  Which style is it in or inspired by?  What type of wood might it be made of?  Where may it have been produced? 

Seat and arm rests are covered in soft brown leather, in fairly good condition.  The back has been unfortunately recovered in plastic (that will need to be re-done!).  Some tacks are missing but can be replaced.  Very comfy to sit on, springs and padding all seem 100%.  Height adjustment works, don’t think it can tilt any more, though.  Or perhaps I have not yet figured out how to make it tilt?

There are no visible markings to go by.