Cotton type rangefinder

[Keith Webb]

Originally Posted by Lang

Keith,

What do you think it was used for? Requiring a known height indicates it is some sort of surveying instrument but 20 feet being the smallest setting - a pretty high pole!

It seems far too accurate and unflexible to be getting distances from guessed object heights so seems to have little field application.

Lang

Have had more of a snoop around the internet and there is one in the Opticalia museum link
It has been shown on one site as having something to do with the military, but it would seem to have more of an application in the surveying field.
The company who made it, E.R. Watts made all sorts of interesting optical things including bomb aiming instruments during the second world war.