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?
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.