The Meaning of BZ

Recently we had a discussion with an “old” Sparker about the use nowadays of the “BZ” as meaning “Well Done” and it’s original wording from the old Fleet Signal Book, before we became “allied”and changed to the ATP1….. when the wording (from memory)
was “Manouver Well Executed”…and we were trying to think of its counterpart group ….was it “BX” or “BW” …Manouver Poorly Executed. Carry it out again””

We also recalled that the Fleet Signal Book had an 8 Lbs (say 2.5 Kilos) sheet of Lead built in to it’s back cover so that it would sink if thrown overboard and that when the Chief Yeoman threw it at you when you mucked up, if you didn’t duck quickly it would knock your head clean off.

Appreciate if anyone can shed light on Bravo Zulu