Re: how do you calibrate Wild optical rangefinder?
On mine, there are two adj on the right side. You kinda have to rotate a little protective sleeve around to expose the other one.
First, get the mirror images in proportion to each other by using on of the knobs on the left. Once you get them to where you see the same amount in the rectangle as you do above it, find an object @ a known distance, set the readout to that distance and adjust the other knob on the right until the images line up (one is on top of tube and other is on bottom, can't remember which is which).
I've always done mine on telephone poles or fence posts. Something that is easy to line up.