Very intriguing tool, but what is it?

[Ed Barry]

Recently I visited Maison de l'Outil (the house of tools) in Troyes, France. This is a museum containing tools from all trades, from coopering to butchering, and lots of woodworking tools. There was one tool that intrigued me more than the others, that being what appears to be a marking tool, possibly an early rafter square. The tool itself appeared to be separable to allow marking of different angles. While I would like to build one of these for myself, I'd like to know what it was used for. Any ideas?

[Alan Schwabacher]

I would guess that it's not designed to separate, but the construction is designed to keep the (presumably 30, 60 90 degree) angles constant, even with crossgrain expansion and contraction of wood with humidity change.

[Moses Yoder]

That looks like a 30/60/90 triangle used for isometric drawing on a drafting table. I agree with Alan, it probably does not come apart.

[John Coloccia]

My first thought was that it was a drafting tool also.

[lowell holmes]

It's not a 30-60 triangle. The hypotenuse on a 30 degree triangle is twice the rise (short side).

I'm guessing it was made for a recurring angle that was not a 30-60. I wonder what they were making.