Q-Top combination panoramic head and quick release mount. Made by a German company - see this Web site: http://www.ideesign.com/id29.htm.

The base part of the head has a bubble level on its top face - a feature extremely useful when a ball head is used on the tripod. A single motion is always sufficient to line up the camera, no matter how crooked the legs of the tripod may have happened to be set as it so often happens when shooting outdoors.

The three circular discs lock the upper portion of the unit (removed for this picture!) in position. They correspond with cam-shaped notches so that locking can take place at a total of 12 positions at 30-degree intervals. The two placed close together are attached rigidly whilst the one adjacent to the release knob moves inwards when the knob is pressed to free the lock.

The small lock safety knob is just faintly discernible at the lower right flank of the blue main body of the unit.