Hi I have a 1970 Mark II Speedmaster which was sold to me as a ‘one owner from new’. The bracelet is stamped 1153/138. The end links are 173. Was this bracelet used by Omega for this watch? My research suggests not.
It has been reported here before that the Mark IIs did often have a buyer requested or dealer preference bracelet. One owner one here had one from new with an 1171 bracelet. It's entirely plausible that yours was sold originally with a dealer fitted 1153 bracelet.