Actually it is an oiler, the glass reservoir allows you to see how much oil is left, and the needle valve is for regulating the amount of oil flow, the open part below is for seeing how big the oil droplets are befor going down the tube into the bearing. these were used alot for old babbited pillow block bearings on equipment such as steam powered saws, horizontal air compressors, pump shafts or any horizontallymounted shaft which needed those type bearings.......