Dalton Adding Machine
"The Dalton was the first ten key adding machine and was introduced in 1902. It went on to become one of the most popular 10 key adders of the time. Earlier models had glass inserts to allow customers to view the gears actually calculating the answers. By the 1920's over 150 models of Dalton had been designed."

Source: This Olde Office

X-Number World of Calculators