USD $179

Originally made by Gilson but sold under a number of different marques (e.g. Post, Dietzgen, Tavella, etc), this 21 scale rule is recognized for its high visibility alternating yellow and white rings.

The rule has unique fractional ‘binary’ scales that permit operations directly with fractional numbers, and also drill size scales. Rotating dual cursors with a slip clutch on one side, and a single cursor on the other.

This specific rule and its case are in above average condition.

Scales include:

**Front** – C, CI, A, K, L, Log Log (1.0015-1,000,000), fractions, fractions, drill/thread, mm

**Back** – degrees, sines, tans, degrees, sines, tans, degrees, sines, tans, Fractional Conversions

**Stock:** 1

USD $149

Originally made by Gilson but sold under a number of different marques (e.g. Post, Dietzgen, Tavella, etc), this 21 scale rule is recognized for its high visibility alternating yellow and white rings.

The rule has unique fractional ‘binary’ scales that permit operations directly with fractional numbers, and also drill size scales. Rotating dual cursors with a slip clutch on one side, and a single cursor on the other.

This rule is in good condition, and the case is in acceptable condition with some fraying and marking.

Scales include:

**Front** – C, CI, A, K, L, Log Log (1.0015-1,000,000), fractions, fractions, drill/thread, mm

**Back** – degrees, sines, tans, degrees, sines, tans, degrees, sines, tans, Fractional Conversions

**Stock:** 1

USD $215

This is a single sided circular slide rule operated by using the two knobs on the top of the rule’s all metal casing. Some details on using these style of calculators can be found here. The Long Scale version of this calculator is specifically designed for use by engineers, draughtsman, and science students.

The designation of “long scale” (also some times called “magnum”) refers to this calculator being 1.5″ larger than the standard Fowlers Calculator, allowing for much finer gradation on the scales, and allowing calculations of four or five significant digits.

**Stock:** 1

USD $249

This is a very rare 4″ pocket circular rule, that comes with both the original factory box and manual in very good condition.

Scales include: A, C, CI, Log, Log-Log, Binary, S,

**Stock:** 1

USD $50

Used for electrical communication engineering, this rule simplifies to one step common calculations that would normally be done in 2-3 steps using a standard slide rule.

**Stock:** 1