Lulu

The schematic for this game identifies the backglass spinner and motor assembly as the "clock unit". The lower playfield inserts numbering 1 through 5 record how many balls drain via the skill holes (aka gobble holes). In another Williams game having this feature, Williams' 1955 'Smoke Signal', a replay is awarded when all five balls drain in this way. Reportedly, the schematic for Lulu does not indicate any reward or other function is tied to the lighting of these five inserts.