|Name and Model Number||Spirule by Walter Evans|
|Country of Origin||U.S.A.|
|Date of Manufacture|
|Front Scales||Specialised Scales|
|Scale Length||29.2 cm|
|Type of Rule||Other|
|Area of Use||Other|
|Comment||Used for addition of angles or multiplication of lengths of vectors.
The Spirule can also be used in plotting vectors or as a circular slide rule.
|Donor||Collection of Rod Lovett|
|RR||= Rare -- 1 of 25 collectors has one; it may take a year to find an example in the marketplace.|
|RRR||= Very rare -- only very few known to collectors; may take several years before one comes up for sale.|
|RRRR||= Extremely rare -- a museum piece; unlikely that an example will ever come up for sale.|