1. This rule was designed for Chemical Engineers and, in addition to "standard" scales, has a number of special scales.
2. On the back, at the top of the stock, is a pair of scales for the atomic/molecular weight of elements and common compounds. The rule use an interesting convention of lines over or under the symbols to aid fixing the decimal point. These are, in effect, a sliding table.
3. There are three scales °F, °C and °K for conversion of units of temperature.
4. There are also three scales, mm Hg, Kg/cm² and in. Hg for conversion of units of pressure.
5. This a scale labelled tw for vapour pressure of water.
6. There is a pair of scales, marked M1 and M2 at one end and Xw and X at the other end. These are used density conversion.