Burroughs 1949
"Just by looking at the grey coloring of this machine, it's not too difficult to date it around the WWII era. An advertisement claims "New square keys add sureness to the touch, wings to the fingers; the machine is pleasing in contour and color; the over-all appearance is an invitation to get work done."
Source: Dr. Tim Bergin, Eric Ashman, Seth Gordon, Jeana Scheirer, Dave Muehling and Andrew Hewitt, "Mechanical Computing."

X-Number World of Calculators