| Name and Model Number | ROSS Precision Computer Type I |
| Country of Origin | USA |
| Date of Manufacture | c. 1915-1919 |
| Front Scales | Spiral scale in 25 revolutions, L scale at edge |
| Back Scales | NONE |
| Scale Length | 9.14-m |
| Type of Rule | Disc |
| Construction | Celluloid disk in 21-cm dia. aluminum frame. Small part of spiral scale visible through celluloid window in aluminum front. Accessory small metal slide rule fastened on front next to window to facilitate approximate values and to indicate which spiral the precise result is on. |
| Area of Use | Generic |
| Comment | Instructions on the handle. Predecessor to more common open-faced Ross spiral slide rule introduced in 1919. This slide rule made in San Francisco for 4 years. |
| Rarity | RRRR |
| Donor | Collection of Ed Chamberlain |
| Match Number | 122 |
| 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. |