| Name and Model Number | Russian Circular Slide Rule Evrika |
| Country of Origin | Soviet Union |
| Date of Manufacture | c. 1930 |
| Front Scales | D, D, L, K, D, D, A, T, °, S, ° |
| Back Scales | None |
| Scale Length | |
| Type of Rule | Disc |
| Construction | Celluloid cursor and disc of diameter 10 cm mounted on plywood base |
| Area of Use | Generic |
| Comment | Designed and evidently also produced by engineer M. G. Braverman. Hand written number 71 on the cardboard case is probably the serial number. The slide rule was also sold without a cursor and that explains the redundancy of scales. A model with 15 cm diameter was also available. Evrika means eureka in English. |
| Rarity | RRR |
| Donor | Collection of Timo Leipälä |
| Match Number | 361
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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.
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