Add-621. American, 2nd quarter 20th century, signed "KEUFFEL & ESSER CO. N.Y., 5704, PAT 1,682,034." Made of black lacquered brass, 5" long x 1/2" square, with a small bubble level mounted on top. The level and its original fitted leather case are in very fine overall condition, in its original cardboard box. When the level is set horizontally, a distant object in the direct sight line is seen through half the tube, and simultaneously the reflection of the bubble appears in the other half when the object and the eye are level.
