| Name and Model Number | Brass Circular Slide Rule |
| Country of Origin | Unknown |
| Date of Manufacture | Unknown |
| Front Scales | D C A |
| Back Scales | none |
| Scale Length | 22 cm (7 cm diameter) |
| Type of Rule | Disc |
| Construction | Brass. 4 parts. No cursor. |
| Area of Use | Generic |
| Comment | Overall diameter 7.6 cm (3")
Acquired from antique shop in Buenos Aires in 1996. |
| Rarity | RRRR |
| Donor | Collection of Antonio C. B. Oliveira, Brazil |
| Match Number | 150 |
| 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. |