Tom, my dad was a YMCA instructor in the 50's-60's and the US Navy Diving Manual was the text book then. There were no slick PADI plastic tables or even C-cards then! I was a PADI teacher you'll probably remember a 3 year window where there wasn't even a swim requirement! I learned from my dad and BC's were 'horse collars' and most people chose not to use them.
Times have changed! (for the better...I like lazing in a BC, totally weightless)