A. Ott polar planimeter
Two Ott polar planimeters
Obtained from the Netherlands
These Ott polar planimeters are from the 1970s and were used for computing area's. The first one shown was from an engineering firm; the second one was used by Delt Hydraulics in hydrography. The last one belonged to the collection of Lodewijk Nienhuis (Lo Nienhuis). Both instruments are very similar but differ in details. They are still very much like the much earlier Coradi instrument also in my collection.
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Two Ott polar planimeters
Obtained from the Netherlands