All Williams games that were released for production were given a sequential Project Number, which is the circled number on the schematic. There is game #362, "500 Auto Race" in between #361 Suspense and #363 Smart Set, the pioneering long-flipper pinball games. Having that number doesn't mean it went into full production, though, as Darts (1971) and Tramway also got those numbers. My guess is that it failed test marketing.
.................David Marston