1. In May/June 2002, my wife and I went for a short break in Germany and hired a car from Europcar. The car came complete with a rechenscheibe - slide rule.
2. On one face there is a scale (in blue) for showing arrival time at a free parking spot in a street. This crafty device means that you cannot get a few extra minutes assuming that the parking superintendent will only pass every 30 minutes or so.
3. On the back there is a circular slide rule for calculating fuel consumption for different distances given the car's fuel economy in litres/100 km. (This method is used on continental Europe rather than the British/US method of miles per gallon.) The calculation of fuel consumption is more important in Germany that in some other countries as it an offence to run out of petrol on a motorway.
4. Unfortunately when we arrived at the airport, there was no-one from Europcar on duty and I was not able to ask permission to keep the slide rule. So, in compensation, let me say that the car worked perfectly, the price we got was the best of several other firms we considered and that we also have had positive experience of using Europcar in the past.