Butt ugly?
OR
Not very accurate?
I'd say it's a level ("niveau") designed for laying out constructed works at a specific gradient. The gradient is set off on the vertical arc and when the level bubble is centered, voila!, the line of sight is at that gradient.
Not exactly sure but this is a modern equivalent (so it claims)
Niveau courtesy Google
It's a rather fine looking bit of gear. Interesting indeed. (Far more than the Android version)
Edit: I'd say Kent is on the ball.
An early clino on a fixed stand/ tripod. Would it have had spiders hairs in the sighting holes?
> An early clino on a fixed stand/ tripod. Would it have had spiders hairs in the sighting holes?
I'm thinking fine wires or threads. You can see horizontal and vertical alignment grooves for the wires etched in both of the two plates with the sighting apertures.
Looks like it might be designed to be on a staff. Could it have something to do with artillery?
Is there too much exposed brass for military use?
Yes, I saw the ball joint too.
> Looks like it might be designed to be on a staff. Could it have something to do with artillery?
I think the range of angles is to small to be useful for artillery. The gradients are more in the public works range: curbs, drains, sewers, railroads, and roads.
Here's a link in French. Bears out most of what has been said above.
http://le.compendium.pagesperso-orange.fr/niveau_lefebvre.htm
The pictures tell the story.
Using Google Translate we get:
HTH,
DMM