This wonderful old thermometer was produced for the Leahy Manufacturing Co. of Higginsville, MO., by the American Thermometer Co. of St. Louis, MO. Leahy Manufacturing Co., established in 1883, produced "the cadillac of incubators" for baby chicks. I am assuming this thermometer was used at one time, in an incubator. It is designed to attach to a surface with screws and protrude from the wall for easy reading. The metal thermometer works perfectly. It measures 4 1/4" long and stands out 3 1/8" from the mounting surface.