Nice clock. And if I were you I would have it service just make sure they know what they are doing there are some incompetent clockmakers out there I know. Also there is a hole on the back I bet that's for adjusting the time for fast and slow and the nob with Omega for winding it and the other plain nob with arrow for setting the time. I am also a clock nut I collect any thing that tells time wristwatches pocket watches and clocks have slowed down on clocks since I moved to MT one thing about Montana there is nobody that repairs them only one watchmaker in Bozeman MT and he stopped working on clocks and some times won't touch some watches I bring in. Been shipping most watches out of state for service kind of a bummer I like doing things local. But great Omega clock your grandfather left you. And I bet it was a shop clock in a store that sold Omega watches.