those are used as the score multipliers. They look like pinball machine score reels 'cause they are ... sorta.
the 2x multiplier is a standard 10 step (0-9 digit) pinball score reel. This unit can handle 2x and 5x multiplying.
the 3x multiplier needs to have some different bits because 10 is not a multiple of 3, so you need either a 9 step unit or a 12 step unit. Afaik, bally always used a 12 step unit since that's also useful for 4x and 6x multiplier needs.
in other words, the two units you have can be wired for 2x, 3x, 4x, 5x for 6x multiplying...and 10x or 12x. A game like the 1008 has five of those score reels in it. two 10-step and three 12 step.
the basic design is:
1] the payout counter unit is electrically stepped.
2] for single coin play (no multiplying), each coin ejected steps the payout counter once.
3] for 2 coin play, each coin ejected steps the 2x unit once. On every other step of the 2x unit, wipers on the unit also connect and step the payout counter. i.e. two steps of the 2x unit results in one step of the payout counter, so payout is doubled.
4] 3 coin play is similar to 2 coin play, but the 3x unit is used and it steps up the payout counter once for each three coins ejected.
the coin/odds unit determines where the hopper switch pulses go (direct to payout counter, or the 2x unit or the 3x unit).
if ya look at the circuit boards on the 2x and 3x units, you'll see how the traces are jumpered together to get an every-other or every-third connection.
there's no "homing" circuit for the 2x or 3x units, so if you manually step them, then the first payout that uses each unit may be short 1 or 2 coins. After the first underpay for each unit, the units are stopped in a good position and all future pays will be correct.
tmi
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the other main way bally did score multiplying with a mechanically stepped payout counter used an odds follower stepper unit. The game literally reset the payout counter and paid again as many times as needed to pay the right amount. The odds follower unit counted how many times the reset/repay happened and stopped doing it at the appropriate time.
games with a replay register and score motor had some other options for payout multiplication, but if the mechines were capable and configured for paying out coins, then coins exiting the hopper had to be what was being counted.