The 5711 always had a modern three-part case construction. The tricky thing about these two-part cases is taking the movement in and out of the case since there's no caseback to be opened. In the old days of the 3700 this was solved via a "split stem" approach that allowed the winding stem
link to well split apart
link from the rest of the watch so that the entire
link movement could then be lifted out of the watch's front side.