If an AD states "applies to Martin model 50 aircraft," to which classification of aircraft does it apply?

The correct classification indicated by an AD (Airworthiness Directive) stating "applies to Martin model 50 aircraft" is that it applies to any and all Martin model 50 aircraft without exception. This includes both standard and experimental certificate aircraft unless specified otherwise in the AD itself. The purpose of such directives is to ensure safety across all applicable aircraft models, and when no qualifiers are provided, it is assumed that every aircraft of that model is affected. Thus, the scope includes all variations of the Martin model 50, ensuring that any necessary safety measures or inspections are uniformly applied to maintain airworthiness.