There are so many variations and models. You really need to talk to someone who is an expert with these.
Talk to Jerry Phillips (215)757-5037 firstname.lastname@example.org
He also has the instructions, conversion charts for yards to meters vice versa etc.
He has a Barrs and Stroud for sale that was his private one that is top notch. He might have a couple others as he deals in them.
Hubie Hakes(go to PA 1000 yard club and email someone and they will give you contact info) has an absolutely pristine Zeiss that is the cleanest set I have ever seen (for $450 in case.