Well through the 1960s Omega shipped watches on leather straps and the customer could at the time of purchase or at any time thereafter add a bracelet of their choice from whatever the dealer had on hand. Sometimes this meant that a older bracelet could find its way onto a more contemporary watch or the inverse, a 1950s watch could be fitted with a newer style, typically when the original strap had worn out or at the time of a routine service.
This is why we sometimes see a flat link 7912, something usually associated with a Speedmaster, fitted to a Seamaster or Constellation.
The bracelet in question is actually from the 1950s and was simply was never as popular as the ubiquitous BOR.
