Transistor Identification using "Q"?

[kt315]

in my opinion TR may be misleaded with TRansformer.

[Kevco]

This is a curious question that came to mind while looking at my daughter's broken stereo, from probably the 1960 or 70s.

I found an online schematic for it, and they used "TR##" to identify transistors on the schematic. Yet, it seems like most schematics I've used over the years, identify the transistors using "Q##". In both cases, the ## being a number for each transistor in the circuit. "TR##" seems to be more appropriate, instead of "Q##", which is common.

The question: where did the practice of using "Q##" to identify transistors come from, rather than using "TR##"? Compare that to resistors being "R##", or capacitors being "C##", etc.

Again, this is nothing serious, but rather more of a curiosity. I can't really think of a reason myself.

Kevco