Original dipstick or in Ford speak "Indicator - Oil Level" for FMX automatic transmissions. Application for 1972 - 1973 Mercury Cougar and Ford Mustang with 351 and FMX automatic transmissions, code "X" on your door data plate.
Sometime during 1972 Ford changed to C9AP-7A020-C. Same dip stick, but with a longer handle.
Ford casting # C9AP-7A020-C.