The expansion of European infrared, optronic and radio-frequency electronics has concentrated attention on detectors, read-out circuits and semiconductor content, where the technology is visibly sophisticated and the policy language is already fluent. Below that level sits a class of components whose apparent simplicity has made it almost invisible to procurement analysis. Sensitive devices must be connected to the outside world, protected from moisture and contaminants, and in a growing number of applications held under a controlled internal atmosphere or a vacuum, while the assembly continues to meet its thermal, electrical and mechanical requirements. Ceramic–metal packages, brazed feedthroughs and glass-to-metal seals perform those functions. Because they can be described in a drawing and photographed on a catalogue page, they invite the wrong procurement question. The question usually asked is whether another European company owns a brazing furnace, works alumina and Kovar, and lists a hermetic feedthrough among its products. That question can almost always be answered affirmatively, and answering it affirmatively explains very little. The question that determines whether European industrial plurality translates into supply security is narrower and harder: on what documented conditions can a second manufacturing configuration — a different producer, a different line, or the same producer’s different site — supply the required part without the customer losing the right to accept it. That question has an answer, and the answer is not a matter of inference. It is published, in ordinary commercial documents, by the customer.