| Name and Model Number | Keuffel & Esser 4133 Roylance Electrical Slide Rule |
| Country of Origin | USA |
| Date of Manufacture | c. 1913-1914 |
| Front Scales | A [B C ] D |
| Back Scales | S L T |
| Scale Length | 20 cm |
| Type of Rule | Slide Rule |
| Construction | Mannhiem style mahogany body with celluloid laminate scale surfaces. The cursor is metal framed with three cursor lines. |
| Area of Use | Electrical |
| Comment | This rule appears in a special addendum of the 1913 catalog introducing the Roylance Electrical Slide Rule |
| Rarity | RRR |
| Donor | Collection of Clark McCoy |
| Match Number | 221 |
| 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. |