Turning the zeroing crank counterclockwise sets the counter digits to zero, while turning it clockwise sets the accumulator digits to zero. Amazing!

Nelson White's U.S. patent "Zero-setting mechanism", filed in 1920, describes how this amazing thing works.

This amazing thing practically never works properly after half a century of neglect.

On the right side of the carriage, unscrew and remove the zeroing crank. Hold the crank while unscrewing.

4-48 machine screw, 1/4"

Zeroing crank