Watts’ SF80-1 parallel plate micrometer in green enameled aluminium. Leather case and strap.
A micrometer is used to improve the accuracy of level reading. This micrometer can be attached to the object lens end of a level and secured in position with the top locking screw (see images 1 and 2). By turning the micrometer knob the internal parallel-sided glass plate is tilted, thereby causing the line of sight to be raised or lowered. The range of displacement is 10 mm.