Well that 'splains why I'd not run into it before... it was an old file I'd reopened, so not real sure what (pose file?) brought it into my scene.    Still somewhat astounded that I’d never seen, nor even heard “animation layers” mentioned here before.  

Was there ever actually any way to see, or modify, the Layered data in P6 - without resorting to hacking the text by hand?

... and I know you can't read all of'em, these days, so thanks again for checking-out my dilemma Ockham!

... and thanks again to CaptainMARC for snapping to the whole "layer" thing as the hidden source of my problem, -- and a belated welcome to the forum.  

(Sheesh... been hanging around here since day-one, and still have to get clued-in -- by a member that just joined!!   DOOH!   What a charmingly helpful neighborhood this still is!)