Early Topcons used an Exakta style external automatic diaphragm mechanism. Topcon had the shutter release on the front of the camera, like the Exakta, but instead of having it on the left side they put it on the right side - hence the diaphragm assembly sticks out of the lens to the right.
It looks like the diaphragm is semi-automatic. The silver lever opens the diaphragm and holds it open until the brass button is pushed, snapping the diaphragm closed; further travel of the brass button pushes out a prong that activates the shutter button on the body of the camera.
Assuming of course that you are talking about the diaphragm control.
If not, Mr. Racer gave you the answer, above: it is a telephoto lens.