These screws go through the playfield from the top and attach the pop bumper bracket to the bottom of the playfield.
They are also used to hold ground wires in backboxes and mount speakers in the lower cabinet on some games.
Fin shank scews are generally used on older machines.
Twist shank screws are generally used on newer machines.
However, both screws will work on any machine. #6-32 thread.
Data East/Sega/Stern #237-5957-00.