Omega Geneve Cal 601

Inherited this watch from my grandad who passed a while back, found out my parents had it tucked away in an old coin box. Can anyone please tell me anything about this watch, I can't find replica pictures anywhere.

I recently had it balenced, the main spring replaced as it was broken and it has a new crown. I've been told its a Cal 601 dates between 1960-1970. I'm trying to find out the year it was released and how genuine the face is as I can not find others like it.

Also would like to know what buckle this would normally take and where to find one?
Lastly, any ideas how much it would be worth?

Thanks

Thanks for the reply. I believe it is gold plated. And unfortunatly I did not have the hindsight to ask the watch maker for pictures of inside. Will be meeting up with them at the end of the week to collect the watch, so I'll ask. Interesting about the face size, I'll have to investigate that and get the measurements.