| Name and Model Number | Keuffel & Esser "American" |
| Country of Origin | USA |
| Date of Manufacture | Pre 1900 |
| Front Scales | A [B C ] D |
| Back Scales | S L T |
| Scale Length | 25 cm |
| Type of Rule | Slide Rule |
| Construction | Mannheim boxwood body with celluloid laminate scale surfaces. The frame is solid and not adjustable like rules after 1900. |
| Area of Use | Generic |
| Comment | This rule does not appear in the catalogs. It is theorized that this was the first slide rule actually produced by K&E in the USA. It is very similar to the later model # 4054. The only thing that identifies this rule is the name on the case |
| Rarity | RRR |
| Donor | Collection of Clark McCoy |
| Match Number | 218 |
| 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. |