I just recently looked at a French built rangfinder for sale, the model was 31. It is a coincidental rangefinder, I think. It is 3 feet long and uses the mirrors in a tube on the ends. I am not at all familiar with these kinds of rangefinders. I checked the range with the dials. it went from 250 yards(yes I was told it is yards) to 8,000. It has two small dials towards the one side that are not used to range the target. Could anyone give me information on these, and if they are accurate. I would also like to know how to calibrate it.