Any Nautical Types Out There?

[Geoff Winnington-Ball (RIP)]

I've come into what we think - through internet research - is an early 19th century octant. I know it's been in my family since the late 1800s. I haven't got any pictures yet, but it looks almost identical to this (scroll down to the bottom):

http://www.lewis-clark.org/content/c...ArticleID=1914

Mine is in what I would call VG-excellent condition, with all bits complete. It needs some cleaning, but otherwise I would consider it fully functional. There are no maker's marks I can find, but basically, we're dealing with an ebony frame with ivory inlays and brass hardware. The scale runs from 0-100 degrees.

How do I get this properly evaluated? I know nothing about this stuff.