"Between 1873 and 1912, Baldwin made several models based on his principle, but the first successful commercial operation happened only when he joined efforts with Jay Randolph Monroe to adapt a full keyboard and started in New Jersey the Monroe Calculating Machine Co. in 1912."

James Redin , "A Brief History of Mechanical Calculators - Part II."

"No details were available with regard to the first three models, which were only manufactured in small numbers. Model D appeared in 1915, model E in 1916, model F in 1917, model G in 1919; then in 1921 the present model K appeared."

Ernst Martin, "The Calculating Machines." 1925.

Photo: Courtesy of Paul Gleim, Hartland, Michigan.

X-Number World of Calculators