One of the divisions in our group is an Avionics company and a strict rule (not sure whether is FAA / CAA mandated) is that if an Avionics LRU or sensor is clearly a non-working demonstrator or an internal Engineering only sample, then it has to have clearly stenciled or engraved, "NOT FOR FLIGHT" on the case. This is naturally to eliminate the risk of two identical modules getting mixed up in stores or dispatch and a faulty one fitted on board an aircraft.

When I ever traveled to customer visits or trade shows I and colleagues had no end of problems taking this in our hand-luggage as inevitably the bag gets pulled at security. The Security person usually pounces on this and gleefully says, "aha, you cannot take this on board, it clearly even says so on the case" and often takes a lot of persuasion to convince them it just means it cannot be fitted on an aircraft but is fine to carry as hand luggage