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Tom, This class designation letter (class letter) list looks like it is from IPC-2612-1, Appendix A, which I have made my comments known to the IPC several years ago. I take and use the class letters per IEEE 315, Clause 22, the official list being Clause 22.4. Here is what the "standard" has to offer versus what you have listed: BR should be D. It doesn't matter what the diode configuration is.
CN should be C. It doesn't matter if the capacitor is fixed value, variable, settable, or multi-element. CR should be D or VR for a breakdown (Zener) diode. D is not used for LEDs, LEDs use class letter(s) DS as they are considered displays. E has 32 items it stands for including antenna, terminal, ferrite bead ring, and miscellaneous electrical part. GN for general network? This is already covered by the class letter Z. Why use two letters when one will do? J is for the most fixed of a mating pair, it does not matter what the gender/sex is or if there is no gender or has both genders. JP is not a standard class letter and should not be used. Use J and P or W if a piece of wire.
L is for an inductor or coil. For bead, ferrite bead, ferrite bead ring, or binocular core use class letter E. MH for mounting hole. I use PTH for plated through hole and NPH for non-plated (through) hole as the opening may be used for other purposes than for mounting. P is for the most movable of a mating pair, it does not matter what the gender/sex is or if there is no gender or has both genders. Two mating connectors that are each on the end of a cable would use class letter P. This means that a P can connect to a P but you would never see a J connecting to a J.
RN should be R. Like for the capacitor it doesn't matter if the resistor is fixed value, variable, settable, or multi-element. RV is for a varistor but not a variable resistor. For a potentiometer or rheostat use class letter R. TP for test point. People use this non-class letter incorrectly. See the note in IEEE 315, Clause 22.4. You should use the class letter E for a test point item. TP is to be used for maintenance diagrams, for instance when you designate the collector of a BJT as a test point. TN for tuner? I don't know what is meant by a tuner. The class letter Z is probably what should be used (general network). TZ for Transzorb. Transzorb is a trade name. These should probably use class letter D as they act like Zener diodes. VR is for a voltage regulator but not for a potentiometer or rheostat, these would use class letter R. X is for a socket. Use XF for a fuse holder, XDS for a lamp or LED holder, XBT for a battery holder.
I always use the example of the traffic sign that is octagonal in shape. It doesn't matter if it says ALTO, HALT, or STOP on the sign, we all know what is meant. If you were driving during a dark night and you came upon a rectangular sign that had STOP on it you might ponder a while on what was meant.
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