Rare set of probably all 3 different plastic Pocket slide rule with sleeve made (sold) by Rista, which is short for the Richel Stam company from Holland. The slide rules are produced in Germany. They share the same German manual (one included) which includes all 3 models; Rietz 11, Electro 22 and Darmstadt 33. So seems to be a complete set. Some of the sleeves and slide rules are also stamped with Dutch firm names. These models are all complete with minimal signs of use and age. They all measure ca 15 cm or 6 inches long. Price is for all 3 together.
Check the attached video on how to work your vintage man tool : slide rule operation instructions!
