Discovered in a thrift shop last week. It’s not exactly a slide rule, although it resembles one. It’s a metric converter, and if the USA ever joins the metric world, these will be in high demand. Get one now while they’re cheap; only 8 Euros on Ebay! This handy tool does a great job and is accurate enough for most applications, unless you are in need of scientific accuracy. To underscore the historical significance of this gadget, the Smithsonian considers it worthy of a webpage. With one moving part, it should last several lifetimes. The sliding cursor is unnecessary, so I don’t count that.