09-021B. American, late 4th quarter 19th century, and signed "HERRING TONNAGE MACHINE, Mfd. by Tool and Die Co. of Baltimore." This very well designed adder is made of nickel-plated cast iron with steel wheels, 7 1/4" x 4 3/4" x 1/4" thick, with the large circle 4 3/16" in diameter, the small circle 2 1/8" in diameter, and an adjustable bar on the side to set the stop against a scale for "Car Resistance - Tons or M's". The interesting and uncommon version of Webb Adder is in very good overall condition.