Ross Precision Computer, Circular / Spiral Slide Rule




Item History & Price

Information:
Reference Number: Avaluer:4289011Modified Item: No
Country/Region of Manufacture: United States
Original Description:
The Ross Precision Computer is a spiral slide rule of unusual complexity.  It is roughly equivalent to the Gilson Atlas in precision, but vastly more complicated in construction.  The Ross first appeared in approximately 1916, and was made until approximately 1938.  The Gilson Atlas came along in 1922, and being far simpler to make, was much cheaper than the Ross.  Gilson may have won the spiral slide rules war, but the Ross is quite an elegant device.
This Ross ...has the zinc alloy main disc, every example of which shows lots of corrosion.  I have included two close-up pictures that show how bad this problem has gotten.  It may be possible to clean this up, but I don’t know how.  Of note, the trig scales are still there in perfect condition on the back of the disc, and the linear slide rule has not lost its cursor.  The leather case is in very good condition.  
This slide rule is from the collection of Robert K. (“Bob”) Otnes, PhD, one of the founding members of the Oughtred Society and the original editor of the Journal of the Oughtred Society.  It is being sold by the Oughtred Society on his behalf.
The Oughtred Society was founded in 1991 by a group of slide rule collectors and is dedicated to the preservation and history of slide rules and other calculating instruments. Membership is open to anyone.  Further information about the Oughtred Society can be found at: http://www.oughtred.org/.
PayPal is the only accepted form of payment.  Buyers within California will be charged 7.25% sales tax.
Shipping will be by USPS Priority Mail.  Shipping charges will be somewhat higher for destinations outside the USA.  




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