c. 1920 Felt & Tarrant ADDING MACHINE - COMPTOMETER Chicago USA $22.50 USD Sold on: 2013-Jul-16 Marketplace: eBay 2 Treasure 0 Trash 100% Detail: The comptometer was the first commercially successful key-driven mechanical calculator, patented in the USA by Dorr E. Felt in 1887. A key-driven calculator is extremely fast because each key adds or ... More Relevance Historical Items
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