[Milsurplus] JAN Nomenclature

[J Forster]

Does anyone know approximately when tubes started being marked  JAN-6SN7
etc. ?

Also, was the component ID used in larger systems such as:

For a tube:

V-A01  through V-A99   where A a circuit area, such as vertical amp,
sweep generator, or power supply, and the digits are a particular
component designator.

Was this a prewar system or was it introduced in WW II.

Thanks,
-John