#6-32 x 3/8" Pan Screw With Locking Washer
This screw and locking washer is commonly used on pinball machines to fasten various items to the playfield
Williams/Bally #4004-01005-06 , #4008-01003-04, Replaces #4006-01017-06 (round head with sems)
Data East / Sega / Stern #232-5201-00