For those interested, I will sell this. Please purchase with the understanding that it is an old item. A name is written on it. AI Summary: This image shows a "slide rule." This is an analog calculator that uses the principle of logarithms to perform calculations such as multiplication and division. It was widely used until around 1980, before the普及 of scientific calculators. The main body has multiple scales engraved on it, and calculations are performed by sliding and aligning the numbers. It is mainly used for calculations up to about 3 significant figures. The slide rule in the image is the type with a conversion table on the back.