The SD 9 (Stocking Dealers) is built on a stainless steel 6906 frame..... came with one 12 round(6906 size/finger rest mag) and one extended 15 round mag w/ the S&W spacer .....

May have missed it in the chart; but believe there was also a SD-40 along with the SD-3

I also have 2 PC 6906s blue over silver...... but subtle differences one has checkered frame ,
one doesn't.....one IIRC has a single right hand safety one has ambi safety...... one had adjustable sights one come with Novak fixed rear....... have never been able to match them to SCS&W descriptions. Both pick up used but unfired...... know that w/ the second one the box was lost at the LGS .......both acquired mid to late 90's.

Note; there is a "Shorty Mark III" in 9mm but I have never seen a reference to a Mark I or Mark II....makes me go hummmmmm.....................now maybe the " 6906 Compact" 9mm is the Mark I but where is the Mark II??????????