From Frank Pierce comes this most interesting information on the state-of-the-art rally calculator of the 1950s and 1960s.  The CURTA calculator was an ingenious device that did mechanically, what our hand-held calculators do electronically today.  Frank was an active rallyist back in the day and he offers this historical perspective on rally calculators before our space program ushered in the miracle electronic age we enjoy today:

More information on rallies:

In the fifties, transistor calculators didn’t exist.  Most rally navigators used a Frederick Post 10″ circular binary slide rule to make time/distance calculations to compare with stop watch readings and determine if you were on time at odometer readings.  Accuracy was good, but not perfect. The only machines available to make accurate multiplication or division calculations were Marchant calculators. It was electrro/mechanical, the size of a typewriter, cost about $1200.00, and ran on 120 volt A.C. power (static inverters were not yet invented).  For the rally pro, there was a small hand-held mechanical made by Contina Ltd. in Mauren, Liechtenstein (no kidding) called a Curta Calculator. It was expensive (about $200.00), but very accurate to eleven decimal places.  It was nicknamed “coffee grinder” because pf a crank on the top, used to make entries.  My 1955 Austin-Healey A100 cost $2950.00 with license and tax (to put “fifties” money in perspective).  You don’t often think about technology advances, but today’s $10.00 digital calculator does the job better (and has memory!)…………Frank Pierce

For a closer look at the Curta rally calculator go to this web site:  http://www.vcalc.net/cu.htm