Is this watch authentic?

Hey all, my grandad gave me this watch and he is also unsure if it is authentic. It's not in the best shape due to him wearing it consistently over several years, I'm not sure the exact time. I would be interested to know if this is a genuine Omega watch or if it is a fake? Either way it had great sentimental value to me so I'm not bothered either way.

Sorry for the naivity aswell, I'm new to watches. Thanks for any help that anyone has.

It will be a nice present for your grandfather to give him an authentic Omega..

Would also be nice to feed the starving people of the world. If one could afford it.