Context: Manufacturers of devices may have their own proprietary numbering system, for example CK722. Since devices are second-sourced, a manufacturer's prefix (like "MPF" in MPF102, which originally would denote a Motorola FET) now is an unreliable indicator of who made the device. Some proprietary naming schemes adopt parts of other naming schemes, for example a PN2222A is a (possibly Fairchild Semiconductor) 2N2222A in a plastic case (but a PN108 is a plastic version of a BC108, not a 2N108, while the PN100 is unrelated to other xx100 devices).

Question: What was once an indicator of the devices creator?
Answer: a manufacturer's prefix

Question: What makes a manufacturer's prefix less reliable?
Answer: devices are second-sourced

Question: What is the marking for a 2N2222A in a plastic case?
Answer: PN2222A

Question: What is a plastic version of a BC108?
Answer: PN108

Question: What manufacturer creates the most devices?
Answer: Unanswerable

Question: What is the marking for a 2N108 in a plastic case?
Answer: Unanswerable

Question: What kind of case is most common?
Answer: Unanswerable

Question: How many naming schemes use an accurate manufacturer's prefix?
Answer: Unanswerable

Question: Who decided what letters were in the manufacturer's prefixes?
Answer: Unanswerable