| Name and Model Number | Tröger Rechenscheiben |
| Country of Origin | Germany |
| Date of Manufacture | c. 1930 |
| Front Scales | C & D |
| Back Scales | none |
| Scale Length | 72 cm on 39 cm diameter Rechenscheibe |
| Type of Rule | Disc |
| Construction | 39 cm dia heavy cardboard disc with painted scale surfaces; 2 disc nested style with knob on reverse to turn the inner disc. |
| Area of Use | Generic |
| Comment | This 39 cm diameter example is shown with its 30 cm and 15 cm diameter baby sisters.
This circular slide rule was made by K. Emil Tröger of Mylau i. Vogtl. (in eastern Germany.) This is a special large size "suitable for people with low vision." More common sizes were 15 and 30 cm diameter. I found this example in a flea market in Germany. I have never seen another example of the 39 cm diameter Tröger Rechensheibe. |
| Rarity | RRR |
| Donor | Collection of Ed Chamberlain |
| Match Number | 201 |
| 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. |