The most noticable is the forward positioning and single-throw action of the clearing handle, something that the Comptometer lacked for another 8 years. It also weighed less at 13 lbs for their 9-column version compared to 17 lbs for an 8-column Compt.
The machine lacked the Compt's "subtraction cutoff" (or "carry inhibit") tabs but included an extra key (next to the 9-key of the high order column) which added 9 to any "hanging one" in the high order register dial for complementary subtaction operations. Strangely, its keystems were vertically oriented unlike either Compts or its own successor models.
As noted elsewhere, this "shoebox" shape was shortly replaced by a model with rounded corners which was produced for some 50 years, sharing the market for key-driven calculators with the Comptometer thereafter.