HP’s most accurate financial calculator, oddly enough, and despite only returning the ceiling of solve-for-n.
4 points
As a surveyor, he probably had an 11c or 15c (the 12c is the financial version of the Voyager series).
Aside: Swissmicro sells a series of voyager clones with modern hardware:
https://www.swissmicros.com/product/dm15l
More info on the original HP calcs:
https://en.wikipedia.org/wiki/Hewlett-Packard_Voyager_series
2 points