If anyone has a chance, I can heartily recommend a visit to the Arithmeum in Bonn. It is a museum of calulation/calculators not only situated in a beautiful building, but also home to many fine and sometimes interactive manual / mechanical calculation devices. Some discrete, but it also houses the world's largest collection of sliderules. There were tons which had very specific usage, e.g. in farming. No clue which are still being used today, but I bet plenty still are.

https://www.arithmeum.uni-bonn.de/en/arithmeum.html