The Oughtred Society is a group of collectors dedicated to the history and preservation of the slide rule. The society is named after William Oughtred, who is generally regarded to be the inventor of the circular slide rule in 1622 and the rectangular slide rule in 1633. Formed in 1991, The Society now has over 350 members throughout the U.S., Europe, and Japan. Membership dues are $35/year ($40 non-US).
If you have an interest in Slide Rule collecting and it's history, join the Oughtred Society. The Society tries to preserve vanishing Slide Rules and provide a history for the interested collector. We also buy, sell, and trade Slide Rules at our annual convention and in several Swap Sheets published throughout the year.
You can learn more about instruments like: "Palmer's Computing Scale. This is a revolving table, for solving mathematical problems, by a simple mechanical process. it consists of logarithmeric combination of numbers, arranged on two circles, one of which revolves within the other; so that, by the simple process of moving a circular card, the relation of the figures to each other is changed, so as to solve the most difficult problems. The invention must come into general use, though we have not learned where they may at present be procured." From Scientific American Vol 1, No 8, which may be seen at the 19th Century Scientific American Home Page.
If you are interested, see www.oughtred.org