Scrimshaw, wood inlay, compass point or sextant?

[ppgs]

This is some type of navigation or drawing tool passed down in my family from my grandfather.  It seems to be made of bone (or ivory) with a carved wooden inlay.  The bone is carved and the straight measurements are marked at 1 inch intervals (divided into 10 spaces).  The measurements on the curved section is marked in 11 segments, each divided by 4.  The piece pivots and the curved part slides nicely through a space in the straight edge.  The pivot pin seems to be made out of metal but is is very small.  One of the straight sides has a small hole is the very bottom where is looks like something could be inserted.

Does anyone have any idea what this might be?  Does it look like it would be really old?  My grandfather and mother have both passed away and I am not sure who else to ask.  Thank you so much for any help you can provide.

Thanks again,
Sean

[talesofthesevenseas]

Oh Good Lord that is lovely!

I think (emphasis on think) what you have there is a protractor, used in drafting or cartography, rather than a sextant, or an octant, used in navigation or surveying. But I could be wrong on that, especially since I'm not locating one quite like yours. I'm still looking and will keep at it.

The folks here at the Compass Museum could probably help you identify what industry it was used in:
http://www.compassmuseum.com/

[talesofthesevenseas]

If I am correct that this is an antique protractor, you would use it like this:

Lay it flat on a piece of paper, with one of the straight edges aligned straight, at 90 degrees to the edge of the paper. Move the other straight piece along the curve, setting it to 45 degrees or whatever angle you need. Then you take your drafting pencil and draw along the angle.

I'm pretty sure this is how it was used, but I'd like to find a similar example before saying that for sure. Still looking as I wipe the drool off my keyboard. LOVE IT!!

[talesofthesevenseas]

This one is a little different, but the principle is the same:

[cogar]

OH my, while I was typing 3 new replies came in, but will post anyway.

That could very well be a nautical "dividing protractor/compass"

Ten (10) grids per inch is quite common on drawing/drafting rulers. (especially if they are metric  )

Is the curved section not actually 12 large segments of 4 small segments each?

And after studying it for almost an hour I am going to make some wild guesses, to wit:  

With 12 large segments it could mean that each of the 12 segment = 7.5 degrees of the 90 degree maxmium arc. (12 x 7.5 = 90)

And the 3 grid marks (separating each of the 4 small segments) would then equal 2.5 degrees of arc.

So, the 1st Grid mark  past the 2nd Large segment mark  would be equal to 17.5 degrees of arc. (2Lsm x 7.5) + (1Gm x 2.5) = (15) + (2.5) = 17.5 degrees

The hole at the end of the straight edge could/would be used for inserting a pencil lead to draw an arc.

[ppgs]

Yes Cogar!  It is 12 segments, exactly - each divided by 4.  That information is so helpful.  I will also try to contact the compassmuseum as talesofthesevenseas suggested.  Thank you so much for spending time to look at it.  If there is interest from anyone else on the board I can take some macro shots and post it.  Any other thoughts would be very helpful.  Thanks.

[waywardangler]

Good Golly Miss Molly!  That is a tool collector's dream item!  I am almost certain it is ivory.  The small hole you referred to is probably for an alignment pin so when it is closed the two arms are held straight and not warp.  Just guessing as all old rules had alignment pins to keep them straight when closed.  I am guessing this is an angle finder such as what a protractor is used for as tales mentioned.  Where was your grandfather's family from?  This may be European.  I have a number of tool books and will browse them later.
That is one beautiful heirloom!  Treasure it!

Are the measurements on the straight edges in cm/mm?  Can you post some closeups?  Where is the hole you are talking about?  I do not find anything exactly like this in any of my books yet.  I am still thinking this is of European origin.

[ppgs]

Wayward and everyone else.  Than you so much for your interest.  I have already learned a lot about this family heirloom which is mysterious to me.  Here are some additional photos with details and a ruler for scale.  The major marks are not inches, they are smaller.   The minor curved marks are smaller than centimeters.  I hope these additional photos are interesting to you.

[ppgs]

Continued...

[ppgs]

Continued...

[waywardangler]

Was anyone in your family in the hat business many years ago?  The inside scale on the curved piece seems to correspond to a scale used to measure hat size.  I am wondering if there are holes in the ends of the straight rules where a circular band may have been fastened at one time.  See photo...

[Chinese Antique Furniture]

Please, please, never sell this little gem!!!!

You are so lucky to have this as a part of your family history. 

I'm with Tales, and wiping the drool off my keyboard.

[cogar]

Looking at the 1st photo with the ruler on it:

a scale on your rule of 42 is equal to:  -3 ½ inches or 8.8 centimeters, or,

36 = 7.6 cm  …..  33 = 7 cm  ….  24 = 5 cm ….  15 = 3 cm

Which don’t make sense to me therefore I will assume you have a “Barnstick” type instrument that could be old as dirt.

Now for those who don’t know what a “Barnstick” is, ….. it is a fairly precise instrument made by farmers of old when they needed to build themselves a barn. Since they didn’t have a tape measure or a rule they would whittle themselves out a pretty new “stick” of wood about ¾ to an inch square and yea long (between 3ft & 6ft, I guess, it didn’t matter). And they would use that Barnstick to measure all the dimensions of their new barn. Like 20 “sticks” long, 10 “sticks” wide and 12 ½ “sticks” high. And they would cut little “notches” all over that “stick” for other dimensions, and thus they could measure how wide or long the boards n’ beams n’ rafters, etc., needed to be cut for building their barn.

Your instrument could be so old that whoever made it chose the “measurement scale” to fit the size of the physical instrument, …… aka: the Barnstick.

Whatta I know, ….. it makes for a cute story. Cheers

[syl]

My guess is it's some sort of carpentry tool. The modern equivalent would be called a bevel square. You set it to the angle of one piece of wood and then transfer and scribe that angle to another piece so you can duplicate it. And since it looks like scrimshaw I'm guessing it was used in boat building.

[ppgs]

That sounds like a good guess, actually.  I live near the Peabody Essex museum in Salem, MA and I think maybe they might be able to ell me more about it.  Everyone here has been so helpful.  I love all of the ideas.  Any other insights would be very welcome!

-Sean