I really don't know the precise function of this one, and neither did the dealer I purchased it from, who used to specialize in old tools! It is clearly a leveling tool, with three legs, so meant to rest on a surface, and the two levels are very very precise, so it was made with exact leveling in mind. (Good for leveling a tabletop for sure.) I like it as an object, and for the impressed type (K & H no less--my initials), and LEVEL spelled out at on one arm of the T. And with wear along the lower half of the length, perhaps suggesting that something rested on top of it? With a "Patent Applied For" mark and a sailing ship hallmark.

5 13/16" x 5 3/8" x 2" t. Surface wear as evident, but sound and very precisely functioning as a level.