Now I understand your confusion, your machine does not have a top box, so you will find all the stuff normally in the top unit underneath the reel mechanism pan, in the back, maybe screwed into the back wall behind the hopper.
This is a buy a pay machine, a very nice machine, and certainly a very collectable in my opinion. Great machine.
So locate your odds unit, and you can unscrew the mounts and pull it down and forward so you can play with it.
Also, remove your coin acceptor and take a picture of behind it so we can see what you have there.
If you open the door and a tilt lite comes on, then look for a push button type switch, perhaps located on the inside of the door hinge. you can wedge that closed perhaps with a matchbook, or change the connection to NO instead of NC. You probably have to get rid of the tilt light before you can coin the coin in switch with your finger. Usually one hand to push closed the hinge switch (tilt switch), and the other hand to push down on coin in switch. If tilt lite comes on or especially stays on, then you will have no coins accepted, probably.
It may be the tilt condition is your problem rather than odds step up problem. If machine tilts allatime then that is what you have to fix.
Again, if you can coin the coin in switch with your finger repeatedly, then you will see if it steps up or not. that way we can bypass the coin path and whatever may be blocking it. Coins, we don't need no stinking coins.(obscure reference to spaghetti western)
Great machine, I am envious.