The bracelet is in silver and onyx. The crown of the watch should also have an onyx cabochon, which is missing here. Definitely an Omega bracelet for this rare De Ville, from the "Jeux d'argent" collection circa 1974.
Wow. Never seen that bracelet before. I do have one of these thick crystal Grima designed Omegas. Technically I believe it's a ladies watch (5xx.xxx reference) , but with an 18mm strap jammed between the lugs it doesn't look too bad & I still wear it occasionally. Very 1970s.