Accession No

6590

Brief Description

the Ross Precision Computer complex slide rule, by Computer Manufacturing Company, U.S.A., c. 1921

Origin

U.S.A.; San Francisco

Maker

Computer Manufacturing Company

Class

calculating

Earliest Date

1919

Latest Date

1921

Inscription Date

1921

Material

plastic (leatherette, other); metal (aluminium, nickel); paper; paint

Dimensions

300mm (height) x 230mm (width) x 20mm (depth)

Special Collection

Provenance

Donated by an individual on or before 15/10/2009.

Inscription

[On case]:
THE ROSS
PRECISION COMPUTER
COMPUTER MFG. CO.
SAN FRANCISCO U. S. A.
PAT. PEND. COPYRIGHTED.
[On rule]:

Description Notes

The Ross Precision Computer complex slide rule, by Computer Mfg. Co., U.S.A., c. 1921.

6590.1: The Ross Precision Computer slide rule, by Computer Mfg. Co., U.S.A., c. 1921. Complex slide rule with functions to multiply and divide; give reciprocals; solve proportions; handle constant multipliers, divisors and ratios; read 5-place logos and anti-logos; solve exponential problems; give 3-place answers instantly; solve expressions like (a x b x c x d) / (e x f x g x h); solve traverses and other trigonometric problems to an accuracy better than 1 minute of arc, or 1 inch per mile. (As listed in 4 page advertisement).

Circular (metal?) dial, mounted on plastic and metal handle, with attached metal slide rule that rotates and can be used alone or with the circular dial for more precise calculations. Handle and metal backing also rotate to give readings. Rear side has 3 holes with give perspective on another dial, with which an additional plastic measure can be rotated to give trigonometrical and other readings. Handle has reminders of how to use to gain the answer for a multiplication, division or proportion problem, as well as thumb nut to lock dial in place when needed. Circular dial has 25 continuous coils painted on.

Comes with a leatherette case with two metal poppers to secure the dial.
Originally cost $28.50.

With original instructions, advertisement and table clamp. Cast iron desk clamp for use with the calculator. Painted black with plastic logo below the thumb-screw (for tightening the rule in place).

6590.2: Four page advertisement for the Ross Precision Computer. First page details users of the computers; its simple construction; problems it can solve; practical uses; mechanical details; their guarantee; the cost and a photograph. Interior A3 spread illustrates various ‘how-to’ instructions for the computer, with illustrations. The rear page contains a letter from Louis Ross, explaining how the Ross Precision Computer is an improvement on many common slide rules by far.

6590.3: 16 page (15 column) instruction booklet for the Ross Precision Computer. Contains (as per the Contents) a general explanation of parts; manipulation, scales, speed etc.; shows basic examples as well as more special examples; auxillary information and practical applications.


Condition: good, complete.

References

Events