Can you determine the airworthiness of the parts shown in the above pictures? By looking at them, by examining their markings, by reviewing their paperwork, by comparing with their TC documents? These are extraordinarily difficult questions; the answers are certainly not intuitive, cannot be discerned by only reading the FARs and can have bad outcomes.
The FAA has issued Advisory Circulars, Notices, articles/informal guidance, lists, and a wide variety of oral opinions issued by knowledgeable field personnel. This library of reference materials is so voluminous and the information provided can be ambiguous/conflicting and confusing. Few aviation experts can authoritatively command, on a real time basis, as parts are inventoried and/or issued for installation on an aircraft. As the four Office of Inspector General notices (below), issued in just the last 6 months, indicate the bad exercise of airworthiness decisions can have criminal implications.
The daily exercise of the privileges of an FAA certificate (Parts 65, 121, 135, 145) can have serious consequences; bad MX errors can result in accidents. Largely due to the high profile nature of and the safety consequences from the Suspected Unapproved Part issues, the DOT Office of Inspector General and other law enforcement offices have been very aggressive pursuing criminal actions against corporations and individuals, with indictments and convictions following. Knowledge of the intricate criteria which differentiate between airworthy and illegal parts is your best, proactive defense against such claims.
An airline or a repair station does not want to get the publicity like the below OIG notice. An individual who holds an Aviation Maintenance Technician certificate is equally susceptible to such allegation. Technical staff and AMTs will be best prepared for their decisions as to SUPs if they are well-educated on this arcane subject.