The D is the 9" model, E 10" and the L 12".
the letter B after any of these means the arm is black instead of the usual dark bronze colour.
In theory if you make a wide enough armboard and have enough plinth width you could fit any of the Jelco 750 series of arms. You'd have to do it a bit like this one though -
viewtopic.php?f=17&t=45637
