| Name and Model Number | EngPen |
| Country of Origin | USA |
| Date of Manufacture | Unknown |
| Front Scales | [C] D L K A |
| Back Scales | |
| Scale Length | 13 cm |
| Type of Rule | Other |
| Construction | Two telescoping metal tubes |
| Area of Use | Generic |
| Comment | An unusual tubular slide rule,
intended to fit over a pencil. See details at https://www.nzeldes.com/HOC/PencilSliderules.htm |
| Rarity | RRRR |
| Donor | Collection of Nathan Zeldes |
| Match Number | 409 |
| 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. |