I need some help from the minds of the internet. I bought this thing at a yard sale - they call them tag sales here in CT. I only paid a buck for it, but it was marked " OLD TOOL" I puzzled over it for a while, then told the seller that I give up - please give me a clue. He said he thought he got it from his father, but he wasn't sure what it was! Dern. It is made of wood, clearly hand made for a very specific purpose. It was well-made from a single piece of maple, and the center piece was jigsawed free, and rivited so that it can pivot only an angle a little wider than 90. A spike-like thing is on a beveled surface on the but end, maybe a scribe or a centering point?
Here is my (very) rough sketch and a couple of pictures.

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You may already have won the $25,000 prize for identifying it, if anyone has offered such a prize. I know I haven't.

Please e-mail me with me any guesses to the origin or use, however far out.

~~~I Gotta Guess~~~