Schaefer pointed out the trouble with the bingo machine id for the obverse symbol 103 on the Fabatus series is the little symbol that (seems?) to connect the ball to the top bar.
I went looking for models of bingo balls that had a square frame around them (not a typical modern feature of mechanical bingo balls).
Here’s one I found being offered for sale with great pics but little historical detail/context.
If the little sticky out thing at the top is part of the ball not part of the frame and not connecting the two, then it might be the box that catches and releases the random ball. That’s a lot of ifs and by no means certain, but until we find an actual archaeological match for the symbol this is the best I’ve got so far.
Clare Rowan drew my attention to this depiction on a ball game machine in the Bode Museum Berlin:
The rest of the reliefs on this machine are as she points out are all chariot related. See tweet thread for more images.