What tool is this ...?

[Fred Perreault]

My wife's grandfather was a registered civil engineer/draftsman. She came by this tool, which is all brass, in a nice well used box, as is the tool well used. Is this some kind of protractor or other drawing tool? Thanks for any help.

[Howard Garner]

Doing a quick search of the web found this

http://kids.britannica.com/eb/art-122552/With-the-three-arm-protractor-often-used-in-marine-surveying
showing how to use it.

A couple more photos
http://media.web.britannica.com/eb-media/34/109834-004-4FA95CD3.jpg
http://farm8.staticflickr.com/7272/7415407530_6edfabe325_z.jpg

Howard Garner
an ex-sailor

[Lee Schierer]

Doing a quick search of the web found this

http://kids.britannica.com/eb/art-122552/With-the-three-arm-protractor-often-used-in-marine-surveying
showing how to use it.

A couple more photos
http://media.web.britannica.com/eb-media/34/109834-004-4FA95CD3.jpg
http://farm8.staticflickr.com/7272/7415407530_6edfabe325_z.jpg

Howard Garner
an ex-sailor

Having never seen one, I was going to say it would be ideal for determining a location based on three lines of bearing such as ship navigation (Pre-gps) or for locating a forest fire based on lines of bearing from three fire towers.

[Mel Fulks]

It looks similar to some old surveying stuff.

[Fred Perreault]

Thanks for all the answers. The vendors' card was inside the box and it advertised the sale, repair and calibration of marine and engineering tools (Boston). It has a vernier scale and a magnifying eyepiece for reading the scales on the brass ring. It has been used a great deal, and was made in Berlin, Germany. The legs are about 13" long and the ring is about 7" in diameter. It all works smoothly and with precision. I had no idea what to look for till the Creeksters sent me in the right direction.

[Jim Matthews]

What does the label inside the box say?

[Howard Garner]

Another good search term is "station pointer"
Brings up several in museums and antique shops.