Aneroid barometers that have not been properly serviced and calibrated may be prone to one or more of the many common faults that are found and the oft-cited Plastic Bag Text is fallible. Buying an instrument that has not been properly checked is therefore a lottery.
An original Negretti & Zambra leaflet c1910 with directions for setting up self-recording barometers (barographs), thermometers (thermographs), etc
The Science Museum recently posted a very interesting blog about the story behind John Harrison and his portrait at the Royal Observatory. In its own way, the invention of the aneroid barometer by Lucien Vidi and its determination of altitude was as significant an invention in the 19th century as Harrison’s was in the 18th. https://blog.sciencemuseum.org.uk/portrait-mr-harrison-timekeepers/