| Name and Model Number | Hiltpold System Ing. E. W. Hiltpold |
| Country of Origin | Switzerland |
| Date of Manufacture | During and just after WWII. |
| Front Scales | A [B C] D L 360° scale |
| Back Scales | K S T ST |
| Scale Length | About 14 cm (CD scales) |
| Type of Rule | Disc |
| Construction | Transparent plastic rotatable scales. White plastic fixed scales. Aluminium core. |
| Area of Use | Generic |
| Comment | Walter Hiltpold (1897-1945), a Swiss engineer from Zürich, obtained two Swiss patents for what he called a Kreisnomograph (circular nomograph); N° 228237 was applied for in 1941 and N° 227376 in 1942, both patents were granted in 1943. Two sizes of this quite clever circular rule are known to have existed, the one pictured is the smallest one (100mm x 75mm overall dimensions). The scales are laid down only on a portion (235°) of the circle. Notice the 360° scale meant to measure angles.
There was an instructions booklet printed in German and a translation of it in French. The early death of the inventor might explain the rarity of this slide rule. See article by Paul Wirz The semi-circular slide rules of Walter Hiltpod in the proceedings of the 4th International meeting of slide rule collectors (available through http://sliderules.lovett.com). |
| Rarity | RR |
| Donor | Photo from a collection in Belgium |
| Match Number | 341 |
| 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. |