Mystery Tool #3

Anyone know what this tool is used for?

A friend has had it in his drawer over 20years and we can't figure it out.

The long shaft rotates and turns the inner dial. The outer dial turns also, slower than the inner.

Whole thing is about length of your hand.

Made by Starrett in USA - www.starrett.com/

 

UPDATE: I found the answer. The response from the Manufacturer is on the Update of this blog post about it: dnwallace.com/blog/2010/02/10/mystery-tool-1/

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Taken on February 10, 2010