Omega Seamaster Calendar Automatic - Owned

Hi Everyone,
I recently found a really old Omega seasmaster lying around in my dad's drawer. It's in a pretty bad condition but is still working(Automatic watch). After searching online I finally came across this forum which has amazing bunch of like minded people who appreciate the real timeless pieces from Omega. It would be great if you could answer few queries that are lurking in my head for sometime.

Some basic information :
1. The strap is not the original one that came with the watch
2. My father claims the watch to be from somewhere around 1960's
3. Yes, It's still working

Question :
1. Is this a real original Omega? The branding on the watch claims to be an automatic seamaster calendar, where as the date dial is missing!
2. My father claims the watch to be around 50-55 years old. Could anyone really estimate the actual age of this watch?
3. If it is real, How much is it worth right now?

I appreciate the help and support you all provide and would be glad to answer any query you might have.

Thank you

Based on those photos it looks authentic. But the dial has been repainted - and the mistake of adding "calendar" was made. This dramatically reduces the value. We can age it better if you can get photos of inside the watch. PLEASE get it serviced before you wear it, otherwise you could do real damage to it.

Value - sent entail and priceless. Cash? Given it is a re dial, less than $400