Please excuse this non-watch/clock posting. But if anyone has information to share about this thing I would appreciate it.

This instrument is about 16+ inches long from the edge of the circle to the end of the folded arms. It is well made of bronze and German silver. While cleaning it I noticed a Japanese inspection character, which now makes it even more interesting!

Thanks for looking. More images to follow.

A closeup of the markings.

An overview.

Something very similar

http://vancouver.en.craigslist.../atq/2220454736.html

Tom has it. Greg, yours is missing some pieces.

Yes, Jim, Tom nailed it. And thank you Tom.

It's a Japanese Imperial Navy navigation instrument used in conjunction with a sextant. The one on Craigs list is different than this one, but clearly for the same general purpose. I suppose something must have fit the hole in the center, maybe a mounting for a chart room table or for the sextant to fit into.

Best regards,
Greg

Greetings

Looks like a protractor which is used for close in coastal navigation/surveying. You'd measure the angle between two objects using a sextant or azimuth circle, dial the angle between the two up on the protractor, lay it on the chart where the arms inner marked went through the references on the chart, and presto you've got your location. Your location would be on the edge which traverses the circle at the halfway point (which is undoubtedly marked on the edge).

These were very important when mapping harbors and depths along the coast, as the depth indicators on the chart needed to be at the absolute point that they were taken and the approach/configuration of the harbor needed to be known in great detail. This is why they have the vernier caliper so that you could dial in the right angle and hold it steady when you marked the position you were interested in.

You'll never see these being used these days when navigating or performing hydrographic surveys, there are simply too many tools at our disposal to do it more accurately.

Nice historical piece, enjoy it and display it proudly.

Michael