I searched scf posts for info on a "D" type but found none. If there is a post I'd appreciate it if I could be directed to it.
The PNC3 2017 Values list does not assign a Type D designation for 1906a but does recognize Type C to have the word "PRECANCEL" in two widths of 13.5 mm - 14.5 mm. I have seen numerous eBay
listings (I think also Hipstamp) listing the 14.5 mm as 1906a Type D.
Both 13.5 mm and 14.5 mm widths appear to have the same font and thick letters. Could this be why the Type D is not recognized as a different type?
Does Scott specialized catalog recognize a Type D? If neither catalog does not, would it be better to not use the Type D term and stick with Type C and just call it "Wide Type C" or other term?
In the photo below it looks to me that the only difference for width is wider spacing between the letters "RE" and "RT" of "PRESORTED".