So let's say I want to keep some transistors on hand

[TinCanAlley]

What's the deal with the part numbers of the transistors in the SM? Is each transistor given a separate number though the same transistor is used in multiple locations? I've been looking at replacements to keep on hand (since they're cheap and it's better to buy more to justify shipping costs) and there are roughly 6 part numbers that correspond to a single transistor (GE-27 is an example).

Also, do the replacement part numbers for other manufactures take into account whether it's a NPN or PNP? The reason I ask is that some of the NTE part numbers note it's it one of a pair of complementary transistors. For those, is there always a complimentary transistor somewhere in the circuit?

Thanks