One of the most versatile tools used by rallyists in the 1950s and 1960s was the Curta Calculator. Often called "The Peppermill" due to its cylindrical shape and the crank on the top, this mechanical device had the advantage of being quite portable, and accurate to several decimal places. Before the dawn of the portable electronic calculator in the early 1970s, all serious rallyists used a Curta in conjunction with a 1/100th reading odometer such as a Halda Twinmaster or Tripmaster.

Curt Herzstark, an Austrian whose family business was the manufacture of calculating machines under license, invented the Curta Calculator. He received the original patents in 1938, but manufacture did not begin until after WWII, in 1947. Contina Ltd., of Vaduz, Liechtenstein, built it. The larger Type II went into production in 1954.

There were two versions of the Curta Calculator, known simply as the Type I and Type II. The Type I, the smaller of the two, has an 8-place setting register, a 6-place indicating dial, and an 11-place answering dial; the corresponding capacities of the Type II are 11, 8, and 15.

The Curta came in a special shock-resistant carrying case, originally made of stamped metal. Later versions had a plastic case. Both opened with a clockwise twist, the reverse of opening jars and most other cylindrical containers. Consequently the opening instructions were printed on the outside of the case.