Pictured on the front page of his tome The Spiritual Taste Described and a Glimpse of Christ Discovered, published in 1649 and engraved by Thomas Cross. Dingley wears a black doublet with a collared cloak, small falling band and black day cap. Note the buttons on the collar and all the way down the front for fastening the cloak for inclement weather, though for the picture, Robert wears it in the off the shoulder manner of religious portraits of the time. Presumably the garment is held on by some kind of strap that fixes around the arms. Although it looks like a coat and it has neck shaping, I believe the wide flap collar at the back marks it as a cloak. Coats at this time generally had no collar or a short stiffened band.
The 1640s Picturebook 