* the case back of such watches are all showing the " seahorse " emblem, since all these watches were originally in the* SEAMASTER * line, although the official name of the Jubilee version is:
SEAMASTER - Speedmaster Professional 125 - chronograph
* it is only much later, when the " chronograph " vogue became so voluminous that we had to separate the sporty SEAMASTER watches from the " chronographs " and give them a separate line !
Above taken from Chronomaddox