There were no transistors during WWII. (The first one was demonstrated in late 1947 apparently.) A valve is a vacuum tube (https://en.wikipedia.org/wiki/Vacuum_tube).

A valve can refer to a vacuum tube or it can refer to a diode, which can be made from all manner of stuff such as razor blades, crystals, rocks. It's called a valve because of its rectifying behavior allowing current through in only one direction, this is also the reason for the diode's electronic diagram icon ---|>|---

Ah bless, tell me your under 60 without disclosing your age.