A signed assemblage by James McNair (1928- ) 
James was an architect who worked in the offices of Phillip Johnson.
This piece and another smaller unsigned example which will be posted in a separate listing come from the estate of Sewell Sillman.
The overall size is 16 1/2" X 16 1/2" X 3 1/2"
Feel free to contact me with any questions about this unique work.