Component value systems, historically?

[Rhodesplyr]

I'm just curious--are there actual *names* for the different component value systems you run into when working on vintage amps?

For example, some older amps have 50k, 75k, or 200k resistors rather than 47k (or 56k), 68k, or 220k. Capacitors go from 0.25uF to 0.22uF and 0.05uF to 0.047uF, etc...

It seems to me that the transition occurs gradually between the second half of the 1940s to around 1960, with resistors changing first.

[Steve Conner]

I don't know what the old system was called, but the new one is the EIA "E series" of preferred values.
Resistor Values E6 E12 E24 E48 E96 E192

[Rhodesplyr]

And even the EIA has evolved. I'd guess it was the RMA when the resistor value change occurred.

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