1. The complex rule was regarded by many as the best rule produced in the US. It is a duplex rule and has 26 scales.
2. It is generally regarded as a "classic" but achieved this status by providing a full range of basic scales rather than any anything out of the ordinary.
3. Comparing it to other classics it could even be considered to lack some scales. Among other features the Pickett N3 includes more complete trig scales and the Faber Castell 2/83N has 20" scales on stock and slide and a P (Pythagorean) scale.