[NA] ID compass / ??

I inherited this device, but can’t figure the purpose of, or how to use one side.
Or the roller at the bottom.
Or what industry might have needed it.
The source is a Navy man.

 

It measures the distance on a map. I have one. Let me see if it has instructions.

I think.

 

The roller, when spun does not appear to do anything.
The distance needle appears stuck.

 

It is called an opisometer. It measures the distance between curved lines on a map. Unstuck, the distance needles would give a distance reading.

 

cool!
Something to look up and learn about.
Will it work on my Garmin moving map?

 

Just as well as on a paper map until you get that needle fixed

 

Have you tried to push the thing on the top or give it a twist or something? Like to reset it to zero?

 

Sounds like something is broken or loose inside.

I have one of these, not exactly the same. I use it to measure trail lengths on maps for hiking.

 

yeah, it does not push/pull but I successfully unscrewed it & it fell off!