| Name and Model Number | Gunter Rule, Sliding |
| Country of Origin | England |
| Date of Manufacture | c. 1800 |
| Front Scales | Inch N [ N N ] SR Mer E*P |
| Back Scales | M:Lon Cho Sin [ Sin Tan ] Tan Sin Tan |
| Scale Length | 28 cm |
| Type of Rule | Slide Rule |
| Construction | Open frame, 30.5-cm long slide rule. Two sided boxwood with brass end posts, no adjustment, and no cursor. Cursor not needed. |
| Area of Use | Other |
| Comment | For navigation & mathematics. The N scales on this slide rule are equivalent to A & B scales. This sliding Gunter is divided on both sides with logarithmic and trigonometric scales, some of which were designed specifically for navigation at sea. The "Sliding Gunter" was designed to supersede the common "Gunter Rule", which required dividers to calculate. The scale arrangement has been attributed to John Robertson, c. 1770s. This Gunter rule can be used to multiply, divide, and for proportional and plane trigonometry calculations. Its principal use was for navigation. Given the "Course" and "Distance", the navigation scales on the sliding Gunter rule could be used to calculate the difference in "Latitude" and "Departure" from one point to another. Undated and unsigned, this example could date to c. 1800.
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| Rarity | RRR |
| Donor | Collection of Ed Chamberlain |
| Match Number | 370
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In conjunction with our 'donors' we assign a rarity rating to each item, based on the system devised by Herman van Herwijnen |
| (1929 - 2004), renowned Dutch collector, author, and creator of Herman's Archive, a collection of 5,000 slide rule images on CD. |
| • RR = Rare - 1 of 25 collectors has one; it may take a year to find an example in the marketplace. |
| • RRR = Very Rare - only a few known to collectors; may be several years before it comes up for sale. |
• RRRR = Extremely Rare - a museum piece; unlikely that an example will come up for sale.
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