Is this Arthur Umanoff?  

I don't see the resemblance....
I don't see the resemblance. In the photos I've seen of Arthur, he seems to be more along the lines of a bipedal humanoid than stationary chair. He alse used a smoking pipe and I dont see any evidence of it anywhere in your photo. (see photo below)

Wow!
Really cool to finally see a picture of this phantom designer. I never read or seen anything about him as a designer or person. I like his stuff alot and he deserves a book of his designs.

Yes Virginia
There is an Umanoff.
The chair is a Arthur Umanoff design for Shaver Howard from the first few years of the Shaver Howard collection.
As far as a book on Umanoff goes I'm more than thinking about it but I couldn't possibly commit to anything until I have the Paul McCobb book out the door.
http://www.arthurumanoff.com

Aak ! So . . .
Umanoff IS de Frutta ! Finally . . .