Difference Engines
A difference engine calculates, and it is the most quietly important machine in the world. Apothecaries use them for dosages and blending, which is part of why the medicine of this world works as well as it does — a dose that varies with whoever measured it kills somebody eventually, and the world worked that out early. Registries use them for records. Counting houses use them for accounts, and Eldershore's handle conversions between four currencies at once without anyone checking the arithmetic afterward.
They are steam-driven. The calculation is gears turning against real resistance, and a hand crank varies with whoever turns it, which is not a quality anybody wants in a machine that decides how much of a chemical goes into a person. So an engine sits where there is already a reason to have a boiler, which is why they are institutional rather than domestic. Nobody has one at home, because nobody has a steam plant at home.
They are clockwork calculators and do exactly what they are set to do. Nobody in the Known World has ever thought them remarkable, which is itself remarkable.