B68-476 MECHANICAL CALCULATOR. Locke Adder. Patented by Clarence Locke of Kensett, IA, in 1901, the Locke Adder was (according to the Smithsonian website) the first American made portable adding machine to enjoy modest commercial success despite its many drawbacks - when the digits on one row go over nine, it doesn't automatically carry over to the next row, and, despite Mr. Locke's claims, it doesn't really work for multiplication and division. He also called it a "pocket calculator" which, since it's 9-3/4" by 4", was maybe true if you're Captain Kangaroo. This is a nice clean example; the black finish on its ornate copper side panels is mostly worn off, but the paint on the sliding bars is intact and they work smoothly. We'll include a copy of the instruction manual that we found online. Good+ 200-400