Chair ID Help - Boris Tabacoff?  

No Idea...
but nothing about them says Tabacoff to me and Ive handled some of his chairs.

Hmm, thanks for replying....
Hmm, thanks for replying. Strange that the seat part looks exactly like the chairs at this link though.
http://www.deconet.com/item/tables/dining-sets/Dining-set-by-Boris-Tobac...

The Plexiglass Seats and...
The Plexiglass Seats and round metal fasteners look identical to the ones in the link.

Maybe not Tabacoff
I work for a company that specialises in mid century modern pieces and based from what I've seen, nothing about these really indicate that they are Tabacoff pieces. Tabacoff's furniture is usually recognisable because of their round, chrome base. Hope that helps!
(edited by DA - link removed)

Is it possible that they are...
Is it possible that they are a prototype?

I have seen a chair in...
I have seen a chair in France wth the crescent base that looks like a tabacoff chair but isn't. I have never seen the perspex tabacoff chairs from your link before. The bases look right, the seat seems like an odd departure in style. I wouldnt be convinced they are tabacoff but it certainly requires more research. Is Boris still alive and kicking ?

To the OP, I only recently came across your post. I have a chair very similar to yours, bought in London in the late 1990s. Did you ever find any information on these mysterious chairs? Here's a couple of pics to compare.