The back contains 3 scales of the following types:
| Type (click to view scale details) |
Range & Units | Numbered | Geometry | Location |
|---|---|---|---|---|
| Degree | 0 - 90, Degrees | Every 5 degrees | Circular, concentric | Cicrular scales located across a large portion of the rim of the back |
| Quadrant arc | 0 - 12, None | Every 3 | Arc | Scales located across large portions of the back of the instrument |
| Unequal hours | 0 - 12, Times of day | Every 2 hours | Arc | Scales located across large portions of the back of the instrument |