This is an example of the Locke Adder, whose sliding rods essentially represent, utilising attractive Victorian scrollwork, an American embodiment of the abacus. The National Museum of American History describes the Locke Adder as follows:
“The first American-made adder to enjoy modest commercial success was developed by Clarence E. Locke (1865–1945). A native of Edgerton, Wisconsin, he graduated from Cornell College in Mt. Vernon, Iowa, in 1892. Locke worked for a time as a civil engineer in Minnesota, and then joined his father operating a lumberyard in Kensett, Iowa. This version of the device has a metal base with grooves for nine sliding metal rods that move crosswise. Each rod represents a digit of a number being added. Protruding knobs on the rods represent different numerals. The rods are held in place by bronze-colored metal covers that extend over the right and left thirds of the instrument. When the device is in zero position, all the rods are in their rightmost position.”
“Numbers are entered by sliding rods to the left, and the result appears in numbers immediately to the left of the cover on the right. The rods are color-coded to distinguish units of money. They lock when depressed, so that they will not slide if the instrument is tilted. The locking mechanism, the color-coded rods, and the oval shape of the knobs on the rods are all improvements featured in Locke’s second calculating machine patent, taken out in 1905. There is no carry mechanism. The base of it is covered with green cloth.”1
1 The National Museum of American History, Kenneth E. Behring Center, “Locke Adder”, http://americanhistory.si.edu/collections/search/object/nmah_690242 viewed 2 Nov 2012. (↑)
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