The bracelet is made by Dennis Shackman and sons in the UK, they made all of the gold bracelets at the time for the UK market for Omega and Rolex/ Longines etc. Swiss Time Service now own their equipment and make solid gold bracelets to order. I am a real fan of these bracelets, they are by far superior to the period Omega stainless steel items (IMHO). I have a few, they only made 18 and 19mm. Yours will fit most omega model from the Seamaster, constellation and Geneve range. Really nice catch, they are rare things