This is an authentic Omega Speedmaster Automatic Chronometer black coloured watch dial that is 31.6mm in diameter and it has patina on its surface. Some watch hand come with this dial.
The writing on your dial reads "Omega, Speedmaster, Automatic, Chronometer, Swiss Made".
I have given you photos of your watch dial from every angle. Please use them to add to this description.
If you are not sure whether this will fit your watch or have any other questions, feel free to message me.