D4 - AN OVERVIEW

*Why "D4"?  I normally get requested,  and will get jumbled with A5 (which happens to be a climbing quality), and D5 (which stood for "Deuce5"), two manufacturers I are actually involved with in the past.  My nickname in Yosemite was "Deucey", coined by Grant Hiskes  who mangled my Friesland ancestral title "Middendorf" to "Dusseldorf",  and D