| Name and Model Number | Keuffel & Essor 4041 With Very Rare Decimal Keeper Cursor |
| Country of Origin | USA |
| Date of Manufacture | 1920’s |
| Front Scales | A B C D |
| Back Scales | S L T located on back of slider |
| Scale Length | 25 cm (10 inches) |
| Type of Rule | Slide Rule |
| Construction | Celluloid on Mahogany – metal framed decimal cursor |
| Area of Use | Generic |
| Comment | Please see my JOS articles on decimal cursors in V18.1-2009-page46. |
| Rarity | RRR |
| Donor | Collection of Clay Castleberry |
| Match Number | 319 |
| 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. |