I came across this thing on amazon.
The device allows to point the camera precisely (to center a mirror image as shown here) by turning the knobs so that the camera swings in two planes, left-right and fore-aft in a vertical setup.
The photo shows the device with max swing in both planes. The base is Arca-Swiss compatible, the screw sticking out at the top has a standard 1/4 inch thread. Max dimensions are 4 in approximately, max load 6 kg.
Here’s an image of the device in use:
