On Fun Land, there is a 0-9 stepper unit that generates the match number. This unit has a bell mounted on it that is sounded by the drive arm of the stepper. The stepper is actuated each time 1 point is scored, so that is where the 1 point bell sound comes from on Fun Land. This setup was a very common practice on Gottlieb games in the 1960s.
The main purpose of an add-a-ball machine was to be legal in jurisdictions where any free game award was considered gambling winnings. As a result, Fun Park doesn't have a 0-9 stepper unit because there cannot be a match feature on an add-a-ball game. So a stand-alone 1-point bell assembly was used for the 1-point bell sound instead.