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The "Schnellkalulator System Bloch" is an unusual device first patented in 1919 and produced over the next few years.  It utilises an approach to evaluating mathematical formulae known as "[[nomography]]".  This is a graphical technique which, having established several parameters in the equation allows one to evaluate the final result.

This particular device quite cleverly implements nomographic principles in a mechanical apparatus to calculate the cutting time required required in turning metal in a machine tool by evaluating the formula involved.  An [[http://sliderules.lovett.com/cookiedev/extendeddisplayarticle.cgi?match=wernerh.rudowskixxxjournaloftheoughtredsocietyvol.14,no.1,spring,2005pg46.1.jpg|article]] by Werner H. Rudowski  explains clearly how this is done.[^Werner H. Rudowski, "The Schnellkalkulator 'System Bloch'", //The Journal of the Oughtred Society//, vol. 14, no. 1, spring 2005, pp. 46-52^] 

Very few of these devices seem to have survived and indeed the author knows of nine [[Bloch Schnellkalulators in Collections]] although there may of course be more.

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See also [[Site.Nomography|Short bibliography]]