I really don't know anything about this one, but found it at Brimfield and couldn't put it down. I presume a ruler or guide of some sort, with the increments along one side approximately one inch and the shorter ones about half an inch. For me the angled lines really make it. lending a sense of movement and three-dimensionality to the whole thing, and the wood, which I think may be boxwood, is lovely. With what looks to be some faint handwritten text in a couple of spots too. 

 15 3/16" l x 2 1/8". Larger increments approx 1"; smaller increments approx 1/2" inch. Very good condition, with definite age to it, I'd guess early 20th c.