Seamaster 600, 1969, originality check?

Hello,
it's my first post, so nice to meet you!
I'll probably not write a lot, but I'll always enjoy some reading.

So, long story short, I've recently bought, at least in theory, an Omega Seamaster from 1969.
I admit that my decision wasn't a very well thought out, but, well, it happened.

I would like to ask if you could take a look at attached photos, and, if possible, confirm (or not) the authenticity of my watch.

I know that dial was replaced (or repainted), I also wonder about lack of engraving on the back of the case, which I somehow missed when looking before buying...

Thank you on advance,
teelfox



Edit: photos made by the seller; I can provide more done by me, if required.