Abstract: A loading and indexing mechanism for loading articles into successive compartments in a circular tray is shown. It is particularly adapted for use with slide transparencies and their circular trays. The mechanism uses a pawl and gear arrangement to catch and hold successive compartments of a tray in registration with the insertion station. Cams are used to cause turning of the axle on which the tray is mounted and engagement and disengagement of the pawl and gear in coordination with each insertion operation.