Burroughs Class 1
"This Burroughs Class 1 was one of the most spectacular adding machines made. It was quite imposing at 19" deep, over a foot tall and more than 63lbs. It had beveled glass walls on 3 sides allowing viewing of the rocking segment mechanism. (The segments and key stops are seen clearly in the front window.)"

David Hicks.

Source: Museum of HP Calculators.

X-Number World of Calculators