Thank you. I was pretty sure I'm not crazy.ScubaPro had a BP/W by 1971 made with a hard plastic (nylon) backpack; we have a perfect unused 1975 set in our shop. The modern BP/W has been used since 1979, starting in use with North Florida cave divers. The major advance was the invention of the v-wedge in the backplate made of metal, which allowed for the tanks to sit stable close to the back-- invented by a then twenty year-old Greg Flanagen in his garage.
As I said in my earlier post I ended up buying the stab around '80. In '05, I went full circle. So has Scubapro it seems.