Often it's a difference in when the bell rings or provision for a tower light.
Mine has no bell. I bought one from KLAR. Mine has a little solenoid that buzzes, I think. I’m hoping I can just hook up the bell to those wires.
the bell is 6V. Almost all the solenoids and relays in the slots are 50V, though a few games used a 6V relay in a lamp flasher circuit.
wire 20 is the 6V power rail, so that almost always connects to one side of the bell. The other side there's color variations, but often it is a solid red wire 10-x.
'course, the 891-14 was different as it had a handle release switch in between the 10-2 wire and the bell :-) The good news - there is a 10-2 wire on the reels, so if your game is the same that wire is there to control the bell for some of the payouts. The 20 relay and jackpot relay also could power the bell.
the bell ringing path to wire 30 goes along wire 20-1 at reel #3 wiper board. The payout relay path to wire 30 is via wire 90. You have to keep those circuits separate in the reels otherwise when you don't have a win, you may wind up with 50+/-6V across the bell depending on the reel wiper positions. The 6V bell coil isn't very happy about that.