Here's a little better look at the mystery item:



A 1028 pixel wide version can be seen here.


The "black box" appears to anodized aluminum and is 18-1/8" long, 1-3/4" thick, and 4-15/16" wide.
The long slot in the black box allows for 7" of travel for that stud.
The short slot in the adjustable platform allows for 2-3/8" of side to side travel.
The rods are approx. 8-1/4" long (measuring from the bottom of the bright platform) and appear to allow about 6-1/8 of maximum travel.
The lowest the platform can go is shown (where that knob comes in contact with the top of the black box).

It is shown attached to the tripod here: