When going through the Fireball machine for the first time, I noticed some cut wires down the right hand side of the cabinet. I made a note of it and moved on. Only later did it occur to me I couldn’t find the knocker.
I went back to those 3 wires and noticed a small metal plate against the side of the cabinet. So this is where the knocker -used- to be. But for some reason, it had been removed.