I have an old German caliper. It works and look like any other caliper but on the other side it has a series of numbers ranging from 0 to 61653. What are these? enter image description here

  • $\begingroup$ It looks like a way to give finer resolution of measurement. On the left it starts @ 0, then the next reading is a 6 on the right side, followed by a 24 of the left & 55 on the right, ... & so on. $\endgroup$ – Fred Apr 7 '17 at 9:45
  • $\begingroup$ Try making a bunch of measurements with both this and a "modern" caliper and see how the numbers relate. $\endgroup$ – Carl Witthoft Apr 7 '17 at 13:39
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    $\begingroup$ The scale is logarithmic, so I wouldn't exclude the chance the caliper doubles as a slide rule. $\endgroup$ – SF. Apr 7 '17 at 15:55
  • $\begingroup$ @SF. you win the nerdjokeoftheweek award $\endgroup$ – Carl Witthoft Apr 7 '17 at 16:34
  • $\begingroup$ very odd that there appear to be no markings on the center slide. Is it possible the device gets disassembled and flipped over to use this scale? $\endgroup$ – agentp Aug 7 '17 at 21:35

Attempting to understand, I finally plugged in a few of the first terms in Sloan's. Sequence A033581 for $6n^2$ is a close match to these terms (within manufacturing precision, the exact numbers could have been put on there to match the actual mark position). $6.1n^2$, rounded up is even closer. No constant in front of n^2 fits precisely, but it's a close fit.

The benefit of this is that it would measure the surface area of a cube whose side was n long. My educated guess is that this can be used to make an estimate for the maximum possible surface area of the object, using the very faded line in the center bar that corresponds to 0 when the calipers are closed. The estimate would assume the object was a cube, with a 10% safety factor to cover irregularities.


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