1. This is the rarer 5" version of the famous 2/83N.  It is a duplex rule with 30 scales.
2. On the front face there are 15 scales.
3. On the rear face there are another 15 scales.
4. Other features include:

• A second tan scale covering the range 41 to 85
• Indication of correction to be applied to common D and LL0 scale
• Use of W scales which give the accuracy of 10" scales on a 5" rule
• Four log-log and four inverse log-log scales