1. This rule has independently rotating pairs of disks on the front and back faces. In both case scales from C inward toward the centre rotate with respect to the scales from D outward.
2. The names of the scales are marked on the cursor on both faces. This feature is useful as it is more difficult to know which scale you should be using on a circular than on a straight slide rule.
3. The rule has an extensive range of trig scales, but does not have a gauge mark for very small angles.
4. The cursor has a hair mark for Ö (4/p).