To completely align a decorative mark or pattern on the inner surface of a case back to the vertical axis at 12:00/6:00 of the watch when the case back is completely screwed.

The watch case includes a middle part for defining a housing 4 closed by a crystal and a case back 6, the case back 6 having a screw thread portion 14 in a first direction. The middle part 2 includes a screw thread portion 16 in a second direction opposite to screw thread direction of the case back 6, and further includes an intermediate element 8 having a first screw thread portion 18 cooperating with the screw thread portion 14 of the case back 6 and a second screw thread portion 20 cooperating with the screw thread portion 16 of the middle part 2.