It looks like a sleeveless tailcoat with an added shoulder cape. From the second image the white parts seem to be an exaggerated collar on his shirt, rather than part of the tailcoat.
Try this pattern
; leave off the lapels, change the shape of the tails, and change out the front button closure for a zipper on the side- Bill doesn't have buttons there. Then look up a tutorial for making sailor collars to use for the cape.
has some lovely shirts with big collars.