The Omega caliber 8521 is an in-house automatic movement found in ladies size Omega watches. This movement was released in 2010.
Omega 8520 VS 8521
There is a similar caliber 8520, with the main difference being that the 8521 is luxury finished with an 18K gold rotor.
In Omega’s Own Words:
Self-winding movement with Co-Axial escapement. Free sprung-balance system with silicon balance-spring. Automatic winding in both directions. Oscillating mass and balance bridge in 18 Ct red gold. Luxury finish with exclusive Geneva waves in arabesque