Omega Caliber Movement's Material

Archer

Movements plates and bridges are mostly made of brass that has been plated. Plating can be of different materials, and in this case it's rhodium plating on the top, with nickel plating under it (can't plate rhodium directly onto brass). Some brands use alternate materials such as German Silver - no silver in this as it's a nickel alloy. So most of what you see there is plated brass, with a few exceptions - the weight on the very perimeter of the rotor is sintered Tungsten, the ball bearing is steel, etc.

The wheels are made of brass for the most part, so the yellow portion of the wheel is brass, and the pinions are made of steel. In some cases other alloys are used such as Glucydur (the balance is Glucydur on this watch certainly), and some watches have gold wheels in some locations. There are other misc. materials used, including alloy for the balance spring (Anachron on this watch), glue that holds that spring in the stud, "rubies" for the jewels (synthetic red corundum)...

Cheers, Al