how do i use this?
 

found this old rangefinder not sure how it works can someone help me?

Not sure how to use it but that last one that sold on ebay brought a whopping $1.24. Look around on Google you will probably come up with something.

It is hard to be sure, but I think that it is one of the early mechanical, optical image alignment rangefinders ... all of which are set manually. This one appears to have a wind drift calculator as well.

If I am correct, you'll have manually calibrate the image alignment .... unless this model has a permanent, non adjustable calibration. I have a similar model that is rated 10 to 65 yards, +/- 3%. I still carry it just in case my electronic range finder craps out. It is very accurate to about 65 yards, but almost impossible t use in low light.

This is a very old technology going back to the early days of the use of artillery in battle. The way it works is optically aligning 2 separate (left-right) "images" of the same object. When aligned perfectly in the viewer, the distance to the object will appear on the range finder's distance indicator, usually in a small glass or clear plastic protected window .... or adjacent to the image as seen through the view port.

Some of these had to be calibrated. This is done best by picking a object at about 50% of the maximum distance rating of the range finder. The instruction book said to calibrate mine at 35 yards. This is done by disengaging the alignment adjustment (usually a wheel or sliding bar) from the distance indicator. On mine this is done simply by pressing a button that frees a geared connection between the distance indicator and the alignment adjustment.

First, rotate or slide the alignment adjustment so that the distance indicator equals the yards you measure to the image. A medium sized tree trunk works great. Then free up the alignment adjustment. Then move the alignment adjustment until the 2 images are absolutely atop one another. Re-engage the alignment adjustment to the distance indicator. Now you should be calibrated. You can test this by stepping away a known distance from an object and using the image alignment to bring the two images together. Then check the distance indicator.

If this one is permanently calibrated, forget the previous paragraph. Simply look through the viewer ... align the two images ... read the distance ... and you are good to go. I am guessing that if you know the magnitude of the x-wind, you simply turn the windage wheel and read how far left or right you have to adjust for the distance to the target.

Now my caveat ... if this thing you have is not essentially like my manual range finder, then I have wasted my time and yours !

had one 30 years ago, not worth the effort to use it