What mechanical component is the heart of the "Leibniz multiplier" capability in the Stepped Reckoner?

Stepped drum or stepped cylinder

The core innovation that endowed the machine developed by Gottfried Wilhelm Leibniz with its superior ability to handle multiplication directly was the stepped drum, also referred to as the stepped cylinder. This component fundamentally changed how multiplication was processed mechanically. Instead of relying solely on simple gears or wheels that needed multiple incremental steps or manual repetitions, the stepped drum featured teeth of differing lengths, specifically indexed to correspond to the numbers one through nine. When an operator engaged a specific position corresponding to a digit, a single action of the crank would advance the result register by the exact required magnitude, eliminating the need for the iterative addition mandated by earlier designs like the Pascaline.