# Silva Polaris compass, use of the second dial numbered from 0 to 7

I am looking for the use of the second (outer) dial numbered from 0 to 7 on the Silva Polaris compass. This second dial rotates independently of the inner dial.

• Please upload a better quality picture that is in focus. I can’t see any example of a Polaris compass with two dials on Google images. Aug 19, 2020 at 15:28
• BTW, the “dial” is called a “bezel”. Aug 19, 2020 at 15:33
• Thanks. I’m intrigued by this. Neither me or my friend (a very experienced mountaineer) have ever seen this or can think what it would be for. Maybe connected to days of the week, but we don’t know how. Aug 19, 2020 at 17:32
• Although he suggests emailing Silva as they’re quite responsive. If you get an answer, please post it here. Aug 19, 2020 at 17:34
• I received a response from Silva : "The Silva Polaris was a Johnson Outdoors manufactured Silva compass that has been discontinued for some time now. Johnson Outdoors is no longer associated with Silva. I am sorry but I do not know the purpose of the second dial. As a long shot, Liberty Mountain in the US used to distribute Johnson Outdoors Silva compasses and now distributes the Swedeish designed ones now. If you reach out to them they may have carried this model at one point. Liberty Mountain" My Quest continue! Aug 19, 2020 at 21:25

It is used to measure distance. You turn it on its side and roll it along a path on the map. This means it has to correspond to a particular map scale (my first guess is 1:50,000, but that looks a bit off). For a different scale you could do a simple conversion.

Can you tell me what the arc length of one major division is? From the picture, it kinda looks like a little more than one inch (maybe 1.25" ?? ). I can get the associated scale from that (i.e. what is the arc length between 6 and 7)

• If you look at the smaller divisions, at the top in the image, they seems to be 1/4 inch, so major division one inch. Aug 20, 2020 at 20:17
• Well done. It is indeed 1 inch between two marks. Thank you for the answer. Aug 20, 2020 at 23:29
• Dang! I was hoping for a slightly different number. The best guess that i have (total WAG) is that the scale is 1:40000 and the major division is for a kilometer, which cant be right because the 1/4 increments don't make any sense for metric. So I still say it is to measure distance, but I am stumped on the scale.
– Mike
Aug 21, 2020 at 2:12
• @Mike - if it is 1" scale will be 1:63,360 or inch per mile - used to be standard in the Commonwealth (e.g. Canada, NZ, AU, UK) before metric conversion. Not sure if the UK still uses this scale as they still use mph on cars AFAIK. I thin US survey is still mile based too.
– bob1
Aug 21, 2020 at 2:30
• I did just find a reference that says "Most of Alaska has been mapped at 1:63,360." which would fit spot on. And I see that Bob beat me to it which makes way more sense.
– Mike
Aug 21, 2020 at 2:31