Abstract: The invention contemplates a machine having serial-number printing capability and comprising a first plurality of print wheels which are serially indexed for each of a succession of input actuations. An indexing pawl has a second plurality of spaced wheel-indexing pawl elements, one for each of a corresponding second plurality of adjacent print wheels. The number of print wheels is greater than the number of pawl elements, and the pawl is mounted for selective longitudinal placement so as to coact with a desired particular second plurality of adjacent print wheels. The print wheels incorporate the feature of selective removal from printing exposure, so that printing need only involve digit indicia on print wheels requisite to serial-number printing at the selected longitudinal region of pawl action.