1091-28 would be a better bet, but it's not that either/anymore since the 1091 is a 3 line machine.
your game glass is a 3 coin multiplier ... which a 1090 is.
it's pretty common for the aftermarket to mix up pieces and rebuild machines to whatever a customer wanted. It's not quite as easy as a game with a solid state processor as the reel wiring and possibly the slotted metal index discs needed to be changed in addition to the glass and reel tapes.
even without schematics, if the game is wired like bally norms checking resistance/continuity per post #2 should tell you something. If it's not clear what to do, pull out the reel mech and take pictures from all sides, especially the reel wiper board wiring and the wiring attached to it at as best an angle as you can to see what rivets the game harness wires attach to.
if you really don't want to see what the M-645-xxx number on the payout disc and the codes stamped into the slotted metal index discs are, there's not much more I can add except you can find schematics on
https://bingo.cdyn.com/slots/I'd suggest you look at the 1090-34 since that is a triple bar machine.