Mid-century modern vintage Zephyr American Autodex desktop directory list finder model S-400.

It it grey in color with a raised rectangular pattern on the top.

This slide-o-magic directory has a sliding key indicator that will point the index to the letter you need and a bar that will pop it open. 

It is new in the original box with instructions and is unused.  Super capacity space for over 1600 listings.

The box is not perfect and has some shelf wear.  Please see photos