Dating curta calculators
Bonhams' upcoming Scientific, Technological and Mechanical Musical Instrument auction in London will showcase a range of rare and unique collectibles, with amputating saws and hand-cranked mechanical calculators all part of the mix.
Enter the handiwork of Austrian-born engineer Curt Herzstark.It's very similar to the 4041 above, but the changes are interesting as shown in these photos (the earlier 40401 is on the on the top).First, it is overall wider, 28mm instead of 25, with the extra space allocated a bigger slide with a large gap between the B and C scales on the slide.This figure can then be multiplied, added to, subtracted from or divided by making changes to a rotating band at the top and then turning the lever.The calculator then cranks out the answer and displays it in a circle of digits on its top surface.
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But after I made new blocks for the cursor and gave the rule a good cleaning, it's back in good form. Interestingly, the fabric-wrapped cardstock case has no labeling, and the bottom of the cursor is imprinted "PAT. They switched to using celluloid blocks by 1916, probably due to costs, but possibly also because those two hunks of metal add a lot of weight to an otherwise light instrument.