[levinll]

Picked this up at a garage sale over the weekend and I've never seen one quite like this before. No name can be found.

 

[DaninVan]

I think that's a really old inclinometer. Looks like its got some history.

Here's a modern version:
https://external-content.duckduckgo...-content/uploads/2013/11/103-2.jpg&f=1&nofb=1

 

[Cherryville Chuck]

I agree with Dan. It looks like it might be scaled to measure pitch instead of degrees. I.E. inches of rise per foot of run.

 

[DaninVan]

May have been used for laying drainage, or landscaping.
Or at least that's what I'd have been using it for.

 

[DesertRatTom]

What a nice instrument/tool. Saved from obscurity.