| Name and Model Number | Wellington, of London A Sector |
| Country of Origin | England |
| Date of Manufacture | 1845 to1855 When Wellington was in business |
| Front Scales | Inches L S C L S C inches (12 inches when folded out straight) |
| Back Scales | I S T T S T T T S N |
| Scale Length | 30 cm (12 inch) |
| Type of Rule | Rule |
| Construction | Solid elephant ivory – brass hinge |
| Area of Use | Technical |
| Comment | Sector – Galileo called his a compass of equal proportions in 1605-10. Used most often for astronomy, navigation, surveying – with proportional dividers. Note the tiny little brass inserts, for using proportional dividers – also note the scales are machine divided and letters and numbers are stamped by hand. |
| Rarity | RRR |
| Donor | Collection of Clay Castleberry |
| Match Number | 329 |
| Thumbnail (Click Picture for Details) |  |
| 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. |