| Name and Model Number | Dempster - Dance |
| Country of Origin | USA, Berkeley, California |
| Date of Manufacture | 1930 |
| Front Scales | Circular C & D scales |
| Back Scales | NONE |
| Scale Length | 23-cm |
| Type of Rule | Disc |
| Construction | 10-cm dia. thin celluloid disk and transparent cursors. |
| Area of Use | Other |
| Comment | Given out as a party favor at the 1930 Engineer's Day Dance at the University of California, Berkeley. John Dempster, the designer of the Dempster RotaRule was a student at UC Berkeley at that time. He had also begun the manufacture of his Model A RotaRule by this time. He probably made this circular slide rule. Note that it is warped due to the use of unstable celluloid plastic. |
| Rarity | RRRR |
| Donor | Collection of Ed Chamberlain |
| Match Number | 116 |
| 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. |