Kilfitt Munchen small camera handle made in the 1950s.  It has a cable release (the long button that comes out of the side of it).  The code name of this part is "Hakli."

It does not have the shoulder rest that it is used with.  The top of it has a tripod screw that would attach to the bottom of a camera or large lens.  The top unscrews and comes off.  The grip itself is hard rubber.  This is very sturdy.  The cable release button pushes in easily and pops back out easily.  There are three holes in the bottom.  The middle hole is threaded.  It is 5 inches long.

This West German Company started by Heinz Kilfitt in 1898 also made lenses, bellows, bellows extensions, and sports scopes, among other things, and was sold to Zoomar Inc. in the early 1970s.