Quoted from MarkG:

Spot Pool was apparently made for export to Italy so it will have subtly different rules than its counterpart Bank Shot. According to the '78 parts catalog, neither game has a Player Unit:..........

Quoted from MarkG:

I suspect that the Ball Count unit is a two solenoid stepper (add and reset).
From what I can tell browsing through the '78 Gottlieb Parts Catalog the only other games that use the same Ball Count unit are single player games made for Italy. There are several Spot Pool owners listed on pinballowners.com (all in Italy) who might be able to send a photo. You could also try asking for one at https://pinside.com/pinball/forum/topic/the-em-seeking-parts-thread
There are many single player, replay (not Add A Ball) games that use the same gear and wiper but a different contact disc. Those would be easier to find if PBR can make you a contact disc.

Quoted from leckmeck:

Starting with Bank Shot, Gottlieb started outfitting their domestic AAB titles with the lightbox advance unit, which is something the Italian exports had for a long time before. I assumed the wiring for these games was probably the same for efficiency in engineering and production, but the different part numbers on the ball count unit are an interesting find, MarkG. I wonder what the difference is in the ball-tracking logic.

Quoted from MarkG:

I believe that Lucky Strike also uses the same Ball Count Unit.
Beware that if you do locate a complete unit from another game the wire colors may not match those in your game. Comparing the schematics of both games will help verify any wire color mismatches. Been there, done that...
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Quoted from illawarra92:

glad you are saving it greg, was so tempted to buy it