Supermarine Chrono GMTA considerable amount of design detail has been carefully incorporated into the 43mm case of the new Supermarine Chrono. The three piece case construction, with DLC coated middle case barrel, follows Bremonts signature design, however the sleek case measuring a mere 15. 8mm is not typical of a sports chronograph which is normally housed in something much thicker. The Supermarine Chrono uses a chronometer rated La Joux Perret 7754 calibre chronograph