Does anyone know what Flanger effect boxes Waylon uses in songs like "Are you sure Hank done it this way" or Rainy day Women?

I always associated Waylon with a phasor, but I could be wrong. A guy I play for sometimes seemed to think it was one of the old Maestro's but I have no way to confirm.

yeah, i was always pretty sure it was a phase also.i'd guess a maestro or mxr,as they were the nashville standards way back.i know dale watson has a phase shifter built in to his new
guitar,& it nails that "waylon-sound".if that helps...?