High back Z chair ?  

while I am no expert,
I have never seen a Selig Z chair in a high back version, nor have I seen one with that slat back variation..I'm not sure what you have is even a Selig chair at all, it's difficult to discern much from the picture.
Can you post a photo of the profile? Does it have any markings ?
Any additional information you can provide would certainly be helpful.
added: I am assuming by Z chair you are referring to Selig's Z chair...

I was referring to the Selig...
I was referring to the Selig z chair. I saved the photo off of a Craigslist add. the other photos would only save as a much smaller file. I agree the slats are to straight. I have decided not to buy it. I did find a Zenith shell I'm going to buy tomorrow. I would post the link, but he sold the chair. Thanks for your input though.

Quite surprised to have found a thread already on this topic, but I have just stumbled across a high-back Z chair on eBay myself. Based upon the matching upholstery and headrest straps, this is either the same chair from this original 2012 post, or a sister chair made by the same company.
The case of this chair is very interesting. Except for the backrest framing panel, the rest of the chair appears to be identical to early Poul Jensen Selig Z chairs with the slotted hole / cinch strap seat support design. The eBay chair has a very old label for "The Backus Brothers" out of Cincinnati. A quick Google search tells me that they were a furniture retailer.
Early Selig chairs were very often unmarked (or sometimes with light impressed stamped letters that are hard to see or wear away over the years).
The backrest panel framing is very simple and does not match the construction style for the rest of the chair.
So either this chair 1) was originally a normal Z-chair bought from BB, then modified by the owner to be high-back, and has appeared twice for sale in the last five years, or 2) BB modified the knockdown construction of the Z chair upon import from Denmark to offer high-back versions through their store.
Not sure if I've come across either scenario for a Danish chair before, but I've got the perfect name for it:
Selig FrankenZtein Chair.

Just noticed that the OP's name has "Ohio" in it, and the current eBay listing seller is in Ohio.
Doesn't answer the question of how it became a FrankenZtein, but thought I'd add it in.

I have absolutely no evidence to say the chair is legitimate, but it feels like it probably is legitimate to me. I guess I like it.